feat: Add configurable maximum search results setting for codebase indexing

[roomote]

Summary

This PR implements a configurable maximum search results setting for codebase indexing, addressing issue #5149.

Changes Made

Backend Configuration System

• Added searchMaxResults property to CodeIndexConfig interface with default value of 50
• Updated CodeIndexConfigManager to handle the new setting with getter method
• Modified codebaseIndexSearchMaxResults schema in types package

Search Implementation Updates

• Updated VectorStore.search() interface to accept configurable maxResults parameter
• Modified QdrantClient.search() implementation to use configurable limit instead of hardcoded MAX_SEARCH_RESULTS constant
• Updated SearchService.search() to pass the configured maximum results to vector store

User Interface

• Added slider control in CodeIndexSettings component allowing users to adjust maximum search results from 1 to 500
• Added localization keys for the new setting

Test Coverage

• Updated all test expectations to include the new searchMaxResults field

Key Features

✅ Configurable Limit: Users can now set maximum search results from 1 to 500 (default: 50)
✅ Persistent Settings: Configuration is saved and restored across VSCode sessions
✅ Backward Compatibility: Existing installations will use the default value of 50
✅ Type Safety: Full TypeScript support with proper interfaces and validation
✅ Test Coverage: All existing tests pass with updated expectations

Testing

• All existing tests pass
• New configuration properly flows from UI → Config Manager → Search Service → Vector Store
• Backward compatibility maintained for existing installations

Fixes #5149

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Important

Add configurable searchMaxResults setting for codebase indexing, updating backend, search implementation, UI, and tests.

• Backend Configuration:
  • Added searchMaxResults to CodeIndexConfig with default 50 in codebase-index.ts.
  • Updated CodeIndexConfigManager to handle searchMaxResults with a getter.
• Search Implementation:
  • Updated VectorStore.search() to accept maxResults.
  • Modified QdrantClient.search() to use maxResults instead of MAX_SEARCH_RESULTS.
  • Updated SearchService.search() to pass maxResults.
• User Interface:
  • Added slider in CodeIndexSettings.tsx to adjust searchMaxResults (1-500).
  • Added localization keys for new setting in settings.json.
• Testing:
  • Updated tests in config-manager.spec.ts to include searchMaxResults.

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