Add OCR Pipeline Extensions developer docs + update vocab-worksheet docs

New: .claude/rules/ocr-pipeline-extensions.md
- Complete documentation for SmartSpellChecker, Box-Grid-Review (Step 11),
  Ansicht/Spreadsheet (Step 12), Unified Grid
- All 14 pipeline steps listed
- Backend/frontend file structure with line counts
- 66 tests documented
- API endpoints, data flow, formatting rules

Updated: .claude/rules/vocab-worksheet.md
- Added Frontend Refactoring section (page.tsx → 14 files)
- Updated format extension instructions (constants.ts instead of page.tsx)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.claude/rules/vocab-worksheet.md

@@ -188,11 +188,35 @@ ssh macmini "docker compose up -d klausur-service studio-v2"
 
 ---
 
+## Frontend Refactoring (2026-04-12)
+
+`page.tsx` wurde von 2337 Zeilen in 14 Dateien aufgeteilt:
+
+```
+studio-v2/app/vocab-worksheet/
+├── page.tsx                 # 198 Zeilen — Orchestrator
+├── types.ts                 # Interfaces, VocabWorksheetHook
+├── constants.ts             # API-Base, Formats, Defaults
+├── useVocabWorksheet.ts     # 843 Zeilen — Custom Hook (alle State + Logik)
+└── components/
+    ├── UploadScreen.tsx      # Session-Liste + Dokument-Auswahl
+    ├── PageSelection.tsx     # PDF-Seitenauswahl
+    ├── VocabularyTab.tsx     # Vokabel-Tabelle + IPA/Silben
+    ├── WorksheetTab.tsx      # Format-Auswahl + Konfiguration
+    ├── ExportTab.tsx         # PDF-Download
+    ├── OcrSettingsPanel.tsx   # OCR-Filter Einstellungen
+    ├── FullscreenPreview.tsx  # Vollbild-Vorschau Modal
+    ├── QRCodeModal.tsx        # QR-Upload Modal
+    └── OcrComparisonModal.tsx # OCR-Vergleich Modal
+```
+
+---
+
 ## Erweiterung: Neue Formate hinzufuegen
 
 1. **Backend**: Neuen Generator in `klausur-service/backend/` erstellen
 2. **API**: Neuen Endpoint in `vocab_worksheet_api.py` hinzufuegen
-3. **Frontend**: Format zu `worksheetFormats` Array in `page.tsx` hinzufuegen
+3. **Frontend**: Format zu `worksheetFormats` Array in `constants.ts` hinzufuegen
 4. **Doku**: Diese Datei aktualisieren
 
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