chore: remove remaining @workspace / vector search dead code

[chungjac]

Remove all code paths related to @workspace (vector/semantic search) that were left after the initial UI removal. This includes:

• localProjectContextController: remove queryVectorIndex, isIndexingEnabled, enableIndexing, GPU/worker thread/cache dir config, onIndexingInProgressChanged, buildIndex('all'). buildIndex now always uses 'default' (repomap only).
• configurationUtils: remove enableLocalIndexing, enableGpuAcceleration, indexWorkerThreads, indexCacheDirPath from config types and defaults
• localProjectContextServer: remove dead config params passed to init()
• triggerContext: remove extractProjectContext and @workspace check
• chatTelemetryController/telemetryService: remove cwsprChatHasWorkspaceContext
• Delete codeSearch.ts (never registered in toolServer, always dead code)
• Update corresponding test files

[codecov-commenter]

Codecov Report

❌ Patch coverage is 33.33333% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 60.44%. Comparing base (f641dc9) to head (2031f58).
⚠️ Report is 9 commits behind head on feature/removing-at-workspace.

Files with missing lines	Patch %	Lines
...sperer/src/shared/localProjectContextController.ts	11.11%	8 Missing ⚠️

Additional details and impacted files

@@                        Coverage Diff                        @@
##           feature/removing-at-workspace    #2687      +/-   ##
=================================================================
- Coverage                          60.46%   60.44%   -0.02%     
=================================================================
  Files                                279      278       -1     
  Lines                              66189    65867     -322     
  Branches                            4243     4211      -32     
=================================================================
- Hits                               40021    39816     -205     
+ Misses                             26084    25967     -117     
  Partials                              84       84              

Flag	Coverage Δ
unittests	60.44% <33.33%> (-0.02%)	⬇️

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