docs: create consolidated feature documentation

Phase 2 (Consolidation) - Feature Documentation Complete

Created 4 comprehensive feature guides:

1. requirements-extraction.md (650+ lines)
   - Complete extraction feature documentation
   - Architecture, workflow, multi-format support
   - Quality enhancement mode, batch processing
   - Configuration, use cases, troubleshooting
   - Provider comparison and optimization tips

2. document-tagging.md (500+ lines)
   - Automatic categorization and tagging system
   - Tag categories: types, domains, priorities, sections
   - Tag-based filtering and analytics
   - Multi-label classification, custom taxonomies
   - Tag-based search and visualization

3. quality-enhancements.md (650+ lines)
   - 99-100% accuracy mode documentation
   - Confidence scoring (0.0-1.0) with 5 levels
   - Quality flags (7 types) and detection
   - Quality metrics and reporting
   - Auto-approval workflow, review automation
   - Custom scoring, integration examples

4. llm-integration.md (700+ lines)
   - Multi-provider LLM support (4 providers)
   - Provider details: Ollama, Cerebras, OpenAI, Anthropic
   - Configuration priority and setup for each
   - Performance comparison and cost optimization
   - Advanced topics: custom providers, caching, token tracking
   - Troubleshooting for each provider

Total: 2,500+ lines of feature documentation
Progress: Phase 2 (Consolidation) 100% complete

Author: vinod0m