docs: add interactive playground and quick start guide

- playground.js: Interaktives Script zum Ausprobieren aller Features
  - Forgejo API Client Demo
  - Post-Listing (53 Posts)
  - Vollständiges Parsing-Beispiel
  - AMB-Metadaten-Analyse mit Validierung
  - Content-Statistiken (Überschriften, Links, Bilder)
  - AST-Struktur-Visualisierung
  - JSON-Export-Vorschau
  - Farbige Console-Ausgabe

- QUICKSTART.md: Schnelleinstieg für Entwickler
  - Playground-Anleitung
  - Code-Beispiele für alle Use Cases
  - Alle verfügbaren Posts aufgelistet
  - Erweiterte Optionen
  - Links zur weiteren Dokumentation

Ready to use! 🚀

QUICKSTART.md

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+# 🚀 Quick Start Guide
+
+## Installation & Setup
+
+```bash
+# 1. Dependencies installieren (schon erledigt ✅)
+npm install
+
+# 2. .env ist schon konfiguriert mit deinem Token ✅
+```
+
+## 🎮 Interaktives Ausprobieren
+
+### Playground starten
+```bash
+node playground.js
+```
+
+Das Playground-Script zeigt dir:
+- ✅ Verbindung zur Forgejo API
+- ✅ Alle 53 Posts im Repository
+- ✅ Vollständiges Parsing eines Posts
+- ✅ AMB-Metadaten-Analyse
+- ✅ Content-Statistiken (Überschriften, Links, Bilder)
+- ✅ AST-Struktur
+- ✅ JSON-Export
+
+### Anderen Post wählen
+
+Öffne `playground.js` und ändere Zeile 64:
+
+```javascript
+// Standard:
+const selectedPost = '2025-04-20-OER-und-Symbole'
+
+// Andere Posts (siehe Liste im Output):
+const selectedPost = '2024-08-05-hello-world'
+const selectedPost = '2024-09-06-OERcamp-Hamburg'
+const selectedPost = '2025-07-02-nostr-schrein'
+```
+
+## 📚 Weitere Beispiele
+
+### 1. Einzelnen Post von Forgejo parsen
+```bash
+node examples/parse-forgejo.js
+```
+
+### 2. Alle Posts auflisten
+```bash
+node examples/list-all-posts.js
+```
+
+### 3. Lokale Datei parsen
+```bash
+node examples/parse-local.js
+```
+
+## 💻 Im eigenen Code verwenden
+
+### Einfaches Beispiel
+
+```javascript
+import { parseMarkdownFile } from './src/index.js'
+
+const result = await parseMarkdownFile('./test/fixtures/example.md')
+
+console.log(result.metadata.name)        // Titel
+console.log(result.metadata.creator)     // Autoren
+console.log(result.content.length)       // Content-Länge
+```
+
+### Forgejo API nutzen
+
+```javascript
+import { createForgejoClient, parseMarkdownString } from './src/index.js'
+
+// Client erstellen
+const client = createForgejoClient()
+
+// Alle Posts auflisten
+const posts = await client.listPosts()
+console.log(`${posts.length} Posts gefunden`)
+
+// Einen Post abrufen und parsen
+const markdown = await client.getPostContent('2024-08-05-hello-world')
+const result = await parseMarkdownString(markdown)
+
+console.log(result.metadata)
+```
+
+### Metadaten extrahieren
+
+```javascript
+import { extractAMBMetadata, validateAMBMetadata } from './src/index.js'
+
+// AMB-Metadaten aus YAML extrahieren
+const metadata = extractAMBMetadata(result.yaml)
+
+// Validieren
+const validation = validateAMBMetadata(metadata)
+console.log(`Gültig: ${validation.valid}`)
+console.log(`Fehler: ${validation.errors.length}`)
+console.log(`Warnings: ${validation.warnings.length}`)
+```
+
+### Content analysieren
+
+```javascript
+import { 
+  extractHeadings, 
+  extractLinks, 
+  extractImages 
+} from './src/index.js'
+
+// Überschriften
+const headings = extractHeadings(result.ast)
+headings.forEach(h => {
+  console.log(`H${h.level}: ${h.text}`)
+})
+
+// Links
+const links = extractLinks(result.ast)
+links.forEach(link => {
+  console.log(`${link.text} → ${link.url}`)
+})
+
+// Bilder
+const images = extractImages(result.ast)
+images.forEach(img => {
+  console.log(`${img.alt} → ${img.url}`)
+})
+```
+
+## 🧪 Tests ausführen
+
+```bash
+npm test
+```
+
+Output:
+```
+✅ Alle Tests erfolgreich!
+✔ 11 Tests passing
+```
+
+## 📁 Verfügbare Posts im Repository
+
+Die ersten 10 von 53 Posts:
+1. `2025-07-02-nostr-schrein`
+2. `2024-08-05-hello-world`
+3. `2024-08-09-sdg-logos`
+4. `2024-08-15-OER-im-Blick`
+5. `2024-09-02-blog_its_jointly_2024`
+6. `2024-09-03-OER-Fachtag-Orca.NRW`
+7. `2024-09-04-OER-erklaert`
+8. `2024-09-06-OERcamp-Hamburg`
+9. `2024-09-11-OER-Brownbag`
+10. `2024-09-15-pirner-oer-youtube`
+
+## 🎯 Typische Use Cases
+
+### 1. Alle Posts mit bestimmtem Tag finden
+
+```javascript
+const client = createForgejoClient()
+const allPosts = await client.getAllPosts()
+
+const oerPosts = []
+for (const post of allPosts) {
+  const result = await parseMarkdownString(post.content)
+  if (result.metadata._tags?.includes('OER')) {
+    oerPosts.push(result)
+  }
+}
+
+console.log(`${oerPosts.length} Posts mit Tag "OER"`)
+```
+
+### 2. Statistiken über alle Posts
+
+```javascript
+const client = createForgejoClient()
+const posts = await client.listPosts()
+
+const stats = {
+  total: posts.length,
+  withAuthors: 0,
+  withLicense: 0,
+  avgContentLength: 0
+}
+
+let totalLength = 0
+
+for (const post of posts.slice(0, 10)) {
+  const markdown = await client.getPostContent(post.name)
+  const result = await parseMarkdownString(markdown)
+  
+  if (result.metadata?.creator) stats.withAuthors++
+  if (result.metadata?.license) stats.withLicense++
+  totalLength += result.content.length
+}
+
+stats.avgContentLength = Math.round(totalLength / 10)
+
+console.log(stats)
+```
+
+### 3. Export als JSON
+
+```javascript
+import { writeFile } from 'fs/promises'
+
+const client = createForgejoClient()
+const markdown = await client.getPostContent('2024-08-05-hello-world')
+const result = await parseMarkdownString(markdown)
+
+// Nur Metadaten exportieren
+const exportData = {
+  metadata: result.metadata,
+  stats: {
+    contentLength: result.content.length,
+    headings: extractHeadings(result.ast).length,
+    links: extractLinks(result.ast).length
+  }
+}
+
+await writeFile(
+  'export.json', 
+  JSON.stringify(exportData, null, 2)
+)
+```
+
+## 🔧 Erweiterte Optionen
+
+### Parser-Optionen anpassen
+
+```javascript
+const result = await parseMarkdownString(markdown, {
+  extractYaml: true,      // YAML Front Matter extrahieren
+  parseGfm: true,         // GitHub Flavored Markdown
+  extractAMB: true        // AMB-Metadaten extrahieren
+})
+```
+
+### Eigene Forgejo-Instanz
+
+```javascript
+const client = new ForgejoClient({
+  baseUrl: 'https://deine-instanz.de/api/v1',
+  owner: 'dein-username',
+  repo: 'dein-repo',
+  branch: 'main',
+  token: 'dein-token'
+})
+```
+
+## 📖 Weitere Dokumentation
+
+- **README.md** - Vollständige Projekt-Dokumentation
+- **docs/ARCHITECTURE.md** - Technische Architektur
+- **docs/DECISIONS.md** - Design-Entscheidungen
+- **test/parser.test.js** - Test-Beispiele
+
+## 💡 Nächste Schritte
+
+1. ✅ Parser ausprobieren (du bist hier!)
+2. 🔜 WordPress Transformer (Phase 2)
+3. 🔜 Nostr Transformer (Phase 2)
+4. 🔜 Batch-Processing
+5. 🔜 Browser-Build
+
+## 🆘 Hilfe
+
+Bei Fragen oder Problemen:
+- Schaue in die Tests: `test/parser.test.js`
+- Lese die Beispiele: `examples/*.js`
+- Prüfe die API-Docs: `README.md`
+
+Viel Erfolg! 🚀

playground.js

@@ -0,0 +1,246 @@
+/**
+ * Interaktives Playground zum Ausprobieren des Parsers
+ * 
+ * Verwendung:
+ * node playground.js
+ */
+
+import { createForgejoClient } from './src/forgejo-client.js'
+import { parseMarkdownString, extractHeadings, extractLinks, extractImages } from './src/parser.js'
+import { validateAMBMetadata } from './src/extractors/amb-extractor.js'
+
+// Farben für Console-Output
+const colors = {
+  reset: '\x1b[0m',
+  bright: '\x1b[1m',
+  green: '\x1b[32m',
+  yellow: '\x1b[33m',
+  blue: '\x1b[34m',
+  magenta: '\x1b[35m',
+  cyan: '\x1b[36m'
+}
+
+function print(text, color = 'reset') {
+  console.log(`${colors[color]}${text}${colors.reset}`)
+}
+
+function section(title) {
+  console.log('\n' + '='.repeat(70))
+  print(title, 'bright')
+  console.log('='.repeat(70) + '\n')
+}
+
+async function playground() {
+  section('🎮 MDParser Playground')
+  
+  print('Dieses Script zeigt die verschiedenen Funktionen des Parsers.', 'cyan')
+  print('Du kannst den Code in playground.js anpassen, um zu experimentieren.\n', 'cyan')
+  
+  // 1. Forgejo Client Setup
+  section('1️⃣  Forgejo API Client')
+  
+  const client = createForgejoClient()
+  print(`✓ Client erstellt`, 'green')
+  print(`  Repository: ${client.owner}/${client.repo}`, 'blue')
+  print(`  Branch: ${client.branch}`, 'blue')
+  
+  // Repository-Info
+  const repo = await client.getRepository()
+  print(`  Beschreibung: ${repo.description}`, 'blue')
+  
+  // 2. Posts auflisten
+  section('2️⃣  Posts auflisten')
+  
+  const posts = await client.listPosts()
+  print(`✓ ${posts.length} Posts gefunden`, 'green')
+  
+  // Die ersten 10 Posts anzeigen
+  print('\nErste 10 Posts:', 'yellow')
+  posts.slice(0, 10).forEach((post, i) => {
+    console.log(`  ${i + 1}. ${post.name}`)
+  })
+  
+  // 3. Einen Post parsen
+  section('3️⃣  Post parsen')
+  
+  // Du kannst hier einen anderen Post wählen!
+  const selectedPost = '2025-04-20-OER-und-Symbole'
+  print(`📄 Parse: ${selectedPost}`, 'yellow')
+  
+  const markdown = await client.getPostContent(selectedPost)
+  print(`✓ Markdown geladen: ${markdown.length} Zeichen`, 'green')
+  
+  const result = await parseMarkdownString(markdown)
+  print(`✓ Erfolgreich geparst`, 'green')
+  
+  // 4. Metadaten analysieren
+  section('4️⃣  AMB-Metadaten')
+  
+  if (result.metadata) {
+    const meta = result.metadata
+    
+    console.log('\n📋 Basis-Informationen:')
+    console.log(`  Titel: ${meta.name || 'N/A'}`)
+    console.log(`  Typ: ${meta.type}`)
+    console.log(`  Lizenz: ${meta.license || 'N/A'}`)
+    console.log(`  Datum: ${meta.datePublished || 'N/A'}`)
+    console.log(`  ID: ${meta.id || 'N/A'}`)
+    console.log(`  Sprache: ${meta.inLanguage ? meta.inLanguage.join(', ') : 'N/A'}`)
+    
+    if (meta.creator && meta.creator.length > 0) {
+      console.log('\n👥 Autoren:')
+      meta.creator.forEach((creator, i) => {
+        const name = creator.name || `${creator.givenName} ${creator.familyName}`
+        console.log(`  ${i + 1}. ${name}`)
+        if (creator.id) console.log(`     └─ ID: ${creator.id}`)
+        if (creator.affiliation) {
+          console.log(`     └─ Affiliation: ${creator.affiliation.name}`)
+        }
+      })
+    }
+    
+    if (meta.about && meta.about.length > 0) {
+      console.log('\n🏷️  Themen:')
+      meta.about.forEach(topic => console.log(`  - ${topic}`))
+    }
+    
+    if (meta.learningResourceType && meta.learningResourceType.length > 0) {
+      console.log('\n📚 Lernressourcen-Typen:')
+      meta.learningResourceType.forEach(type => console.log(`  - ${type}`))
+    }
+    
+    // Validierung
+    const validation = validateAMBMetadata(meta)
+    console.log('\n✓ Validierung:')
+    console.log(`  Status: ${validation.valid ? '✅ Gültig' : '⚠️  Unvollständig'}`)
+    if (validation.errors.length > 0) {
+      console.log(`  Fehler: ${validation.errors.length}`)
+      validation.errors.forEach(err => console.log(`    - ${err}`))
+    }
+    if (validation.warnings.length > 0) {
+      console.log(`  Warnings: ${validation.warnings.length}`)
+      validation.warnings.slice(0, 3).forEach(warn => console.log(`    - ${warn}`))
+      if (validation.warnings.length > 3) {
+        console.log(`    ... und ${validation.warnings.length - 3} weitere`)
+      }
+    }
+    
+    if (meta._warnings && meta._warnings.length > 0) {
+      console.log('\n⚠️  Parser-Warnings:')
+      meta._warnings.forEach(w => console.log(`  - ${w}`))
+    }
+  } else {
+    print('⚠️  Keine Metadaten gefunden', 'yellow')
+  }
+  
+  // 5. Content-Analyse
+  section('5️⃣  Content-Analyse')
+  
+  console.log('📝 Content-Statistik:')
+  console.log(`  Länge: ${result.content.length} Zeichen`)
+  console.log(`  Zeilen: ${result.content.split('\n').length}`)
+  console.log(`  Wörter (ca.): ${result.content.split(/\s+/).length}`)
+  
+  // Überschriften
+  const headings = extractHeadings(result.ast)
+  console.log(`\n📑 Überschriften: ${headings.length}`)
+  headings.forEach(h => {
+    const indent = '  ' + '  '.repeat(h.level - 2)
+    console.log(`${indent}H${h.level}: ${h.text}`)
+  })
+  
+  // Links
+  const links = extractLinks(result.ast)
+  if (links.length > 0) {
+    console.log(`\n🔗 Links: ${links.length}`)
+    links.slice(0, 5).forEach(link => {
+      console.log(`  - ${link.text || 'Kein Text'}`)
+      console.log(`    → ${link.url}`)
+    })
+    if (links.length > 5) {
+      console.log(`  ... und ${links.length - 5} weitere`)
+    }
+  }
+  
+  // Bilder
+  const images = extractImages(result.ast)
+  if (images.length > 0) {
+    console.log(`\n🖼️  Bilder: ${images.length}`)
+    images.forEach(img => {
+      console.log(`  - ${img.alt || 'Kein Alt-Text'}`)
+      console.log(`    → ${img.url}`)
+    })
+  }
+  
+  // 6. AST-Struktur
+  section('6️⃣  AST-Struktur (Auszug)')
+  
+  console.log('🌲 Root-Node:')
+  console.log(`  Type: ${result.ast.type}`)
+  console.log(`  Children: ${result.ast.children?.length || 0}`)
+  
+  if (result.ast.children && result.ast.children.length > 0) {
+    console.log('\n  Erste 5 Child-Nodes:')
+    result.ast.children.slice(0, 5).forEach((child, i) => {
+      console.log(`    ${i + 1}. ${child.type}`)
+      if (child.depth) console.log(`       └─ depth: ${child.depth}`)
+      if (child.value) {
+        const preview = child.value.substring(0, 50)
+        console.log(`       └─ value: "${preview}${child.value.length > 50 ? '...' : ''}"`)
+      }
+    })
+    if (result.ast.children.length > 5) {
+      console.log(`    ... und ${result.ast.children.length - 5} weitere`)
+    }
+  }
+  
+  // 7. Rohdaten-Export
+  section('7️⃣  JSON-Export')
+  
+  const exportData = {
+    metadata: result.metadata,
+    content: result.content.substring(0, 500) + '...',
+    stats: {
+      chars: result.content.length,
+      lines: result.content.split('\n').length,
+      headings: headings.length,
+      links: links.length,
+      images: images.length
+    }
+  }
+  
+  console.log('📦 Export-Vorschau (erste 500 Zeichen Content):')
+  console.log(JSON.stringify(exportData, null, 2))
+  
+  // 8. Tipps
+  section('💡 Tipps zum Experimentieren')
+  
+  print('Du kannst dieses Script anpassen:', 'cyan')
+  console.log('\n1. Anderen Post wählen:')
+  console.log('   const selectedPost = "2024-08-05-hello-world"')
+  
+  console.log('\n2. Mehrere Posts analysieren:')
+  console.log('   for (const post of posts.slice(0, 5)) { ... }')
+  
+  console.log('\n3. Parser-Optionen anpassen:')
+  console.log('   const result = await parseMarkdownString(markdown, {')
+  console.log('     extractYaml: true,')
+  console.log('     parseGfm: true,')
+  console.log('     extractAMB: true')
+  console.log('   })')
+  
+  console.log('\n4. Weitere Funktionen ausprobieren:')
+  console.log('   import { extractYAML, hasYAML } from "./src/index.js"')
+  
+  section('✅ Fertig!')
+  
+  print('Viel Spaß beim Experimentieren! 🎉', 'green')
+  print('Für mehr Infos: README.md oder docs/ARCHITECTURE.md\n', 'cyan')
+}
+
+// Fehlerbehandlung
+playground().catch(error => {
+  console.error('\n❌ Fehler:', error.message)
+  console.error(error.stack)
+  process.exit(1)
+})