Refactor extension architecture and improve reliability/security hardening

[nirajkvinit]

Summary

This PR modularizes the extension codebase and adds reliability/security hardening for file decoration updates in large or high-churn workspaces. Read CHANGELOG.md for more detailed information about the fixes

What Changed

• Split monolithic logic into focused modules:
  • LineSight/src/cache.ts
  • LineSight/src/concurrency.ts
  • LineSight/src/config.ts
  • LineSight/src/constants.ts
  • LineSight/src/decorationProvider.ts
  • LineSight/src/fileFilter.ts
  • LineSight/src/fileWatcher.ts
  • LineSight/src/initialization.ts
  • LineSight/src/lineCounter.ts
  • LineSight/src/state.ts
  • LineSight/src/timer.ts
  • LineSight/src/types.ts
• Kept LineSight/src/extension.ts as a thin entrypoint.
• Added bounded LRU caches for metadata/count/decoration storage.
• Added concurrency limiter with queue bounds and sync-throw safety.
• Added stale-result protections around in-flight decoration counting.
• Added queue caps + coalescing behavior for update storms.
• Added workspace trust-aware startup behavior.
• Added config normalization/hardening for folder/extension settings.
• Added unit test setup with Mocha and VS Code mocking.
• Added tests for cache, concurrency, config, filtering, line counting, and timer logic.
• Updated package scripts and changelog.

Why

• Improve maintainability and testability.
• Prevent extension-host pressure in large repositories.
• Reduce race-condition/stale-cache issues in async decoration flows.
• Strengthen secure-by-default behavior in untrusted workspaces.

Validation

• npm test passes (compile + lint + unit tests).
• Unit coverage added across core pure/utility modules.
  

Notes / Follow-ups

• Potential follow-up: guard refresh command behavior in untrusted workspaces.
• Potential follow-up: add targeted tests for provider/watcher race/overflow paths.