fix: remove cached mcpClient in diagnostic tracking to prevent stale references (#727)

* fix: remove cached mcpClient in diagnostic tracking to prevent stale references

Resolves TODO comment about not caching the connected mcpClient since it can change.

Changes:
- Remove cached mcpClient field from DiagnosticTrackingService
- Add currentMcpClients storage to track active clients
- Update beforeFileEdited, getNewDiagnostics, and ensureFileOpened to accept client parameter
- Add backward-compatible methods to maintain existing API
- Update all callers to use new methods
- Add comprehensive test coverage

This prevents using stale MCP client references during reconnections,
making diagnostic tracking more reliable.

Fixes #TODO

* docs: add my contributions section to README

Add fork-specific section highlighting:
- Diagnostic tracking enhancement (PR #727)
- Technical skills demonstrated
- Links to original project and my work
- Professional contribution showcase

* revert: remove README.md contributions section to comply with reviewer request

- Remove 'My Fork & Contributions' section from README.md
- Keep README.md focused on original project documentation
- Maintain clean, project-focused README as requested by reviewer

README.md

@@ -331,7 +331,8 @@ For larger changes, open an issue first so the scope is clear before implementat
 - `bun run build`
 - `bun run test:coverage`
 - `bun run smoke`
-- focused `bun test ...` runs for touched areas
+- focused `bun test ...` runs for files and flows you changed
+
 
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