fix: use stable cache key for SSH remote workspaces

[roomote]

Summary

This PR fixes the issue where codebase indexing starts from scratch after closing VS Code when using SSH remote connections.

Problem

When using VS Code Remote SSH, the workspace path might be different between sessions (e.g., due to different temporary mount points or path variations). Since the cache file name was generated using a hash of the workspace path, a different path would result in a different cache file, causing the indexing to start from scratch.

Solution

Instead of using just the workspace path for the cache key, we now use a composite key that includes:

1. The workspace folder name
2. The relative path from the home directory (when the workspace is under the home directory)

This creates a more stable cache key that persists across SSH sessions where the absolute path might change but the relative structure remains the same.

Changes

• Modified CacheManager to generate a stable cache key using workspace name and relative path
• Added comprehensive tests for the new cache key generation logic
• All existing tests pass without regression

Testing

• Added new tests to verify cache key generation for workspaces under and outside the home directory
• All code-index tests pass successfully (129 tests)
• Linting and type checking pass

Fixes #6066

---

Important

CacheManager now generates stable cache keys for SSH remote workspaces, preventing unnecessary re-indexing.

• Behavior:
  • CacheManager now generates a stable cache key using workspace name and relative path in cache-manager.ts.
  • Fixes issue where codebase indexing restarted due to different cache keys across SSH sessions.
• Testing:
  • Added tests in cache-manager.spec.ts for cache key generation under home and outside home directory.
  • All existing tests pass without regression.
• Misc:
  • Mocked os.homedir() in cache-manager.spec.ts to return a consistent home directory for testing.

^{This description was created by for 743dc97. You can customize this summary. It will automatically update as commits are pushed.}