Display aggregated file paths for duplicate content chunks

[kapral18]

Problem

When the indexer aggregates file paths for identical content (see elastic/semantic-code-search-indexer#121), the MCP server needs to display this information properly to users.

Currently, search results show a single filePath. After the indexer change, documents will have:

• filePaths: array of { path, startLine, endLine } objects
• fileCount: total number of files containing this content

Proposed Changes

Update search result format:

Before:

{
  "score": 0.92,
  "content": "useContext(JobCreatorContext)",
  "filePath": "ml/pick_fields_step/rare_field/rare_field.tsx",
  "startLine": 18,
  "endLine": 18
}

After:

{
  "score": 0.92,
  "content": "useContext(JobCreatorContext)",
  "fileCount": 77,
  "filePaths": [
    "ml/pick_fields_step/categorization_view/top_categories.tsx:23",
    "ml/pick_fields_step/influencers/influencers.tsx:31",
    "ml/pick_fields_step/rare_field/rare_field.tsx:18",
    "... and 74 more"
  ]
}

Implementation:

1. Update semantic_code_search.ts result mapping to include filePaths and fileCount
2. Format filePaths as path:startLine strings for readability
3. Truncate to first 10 paths if fileCount > 10, append "... and N more"
4. Backward compatibility: handle documents with old filePath field (single string) during migration period

Related

• Indexer changes: bug: documents with identical content overwrite each other - only one file discoverable via search semantic-code-search-indexer#121

Acceptance Criteria

• Search results include filePaths array and fileCount
• File paths formatted as path:line for readability
• Results truncated to 10 paths with "and N more" suffix when needed
• Backward compatible with old single-filePath documents during migration