chore: remove remaining @workspace / vector search dead code (#2687)

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

Author: chungjac