Fix 30 NLP edge cases in Grammar, Spelling, and Punctuation (Phase 10 results and Extension UI improvements)

Fix: TerminalPunctuationGuard for short phrases and comprehensive Nasb/Jazm grammar rules fixes

fix: PDF dropdown visible + verify spelling context + araspell audit - Fix summary export dropdown clipping (overflow: visible + opens upward) - Verify: use_contextual=True in araspell_service.py (line 83) ✓ - Verify: ContextualCorrector fully initialized and used in pipeline ✓ - Verify: All araspell_rules.py classes used: AraSpellPostProcessor, ErrorClassifier, RulesBasedCorrector, OutputValidator, VocabularyManager, WordAligner, SplitMergeSpecialist, EditDistanceCorrector, ContextualCorrector, ArabicSpellChecker ✓ - Fix misleading comment about contextual=False

feat: Enable ContextualCorrector (BERT MLM) for spelling - Pre-download AutoModelForMaskedLM in Dockerfile

feat: Add AraSpell spelling correction endpoint (POST /api/spelling) with lazy model loading - Extract AraSpell pipeline into src/nlp/spelling/ (araspell_rules.py + araspell_service.py) - Pre-download AraBERT encoder-decoder + checkpoint in Dockerfile - Lazy load on first request, contextual=False to save RAM - Update health check to report spelling status