feat: Progressive on-demand wildcard loading system
Implement memory-efficient progressive loading for large wildcard collections (10GB+).
Closes #1137
## Key Changes
- **LazyWildcardLoader**: On-demand loading proxy with thread-safe caching
- **Auto mode detection**: Full cache (<50MB) or on-demand (≥50MB), configurable via `wildcard_cache_limit_mb`
- **Performance**: Startup 20-60min → <1min, Memory 5-10GB → <100MB, Size calc <1sec
- **API**: `/impact/wildcards/list/loaded` - Progressive tracking endpoint
- **UI**: Real-time status (🔵 On-Demand / 🟢 Full Cache) with loaded count
- **Compatibility**: Backward compatible, all existing features work unchanged
## Implementation
- YAML pre-loaded (keys in content), TXT on-demand (path = key)
- Early termination size calculation, transitive wildcard support maintained
- 15 test files with comprehensive documentation
🤖 Generated with [Claude Code](https://claude.com/claude-code)
Co-Authored-By: Claude <noreply@anthropic.com>