Based on PR #7309 discussion and validation from @adamhill, Swift parser is stable and functional. The assumption about parser instability was incorrect.
Changes:
- Removed Swift from fallbackExtensions list in supported-extensions.ts
- Updated tests to expect Swift to use proper parser instead of fallback
- Added comprehensive documentation of lessons learned in docs/lessons-learned/
This ensures Swift files use the proper tree-sitter parser for code indexing.