refactor(repo-search): compose SDE search and minify repository search output

[sanzog03]

Summary

This PR reduces MCP/tool response payload size for RepositorySearchTool to control context growth and token cost.
It refactors the tool from inheritance to composition and enforces a strict minified output schema.

What it does

• Refactors RepositorySearchTool to compose SDECodeSearchTool instead of extending it.
• Minifies each result item to only:
  • url
  • full_text
  • reliability_score
  • repository_metadata
• Removes legacy/heavy response fields from repository search output (title, query, content, extra, etc.).
• Preserves GitHub metadata enrichment and reliability scoring behavior.
• Adds stricter GitHub URL parsing for metadata enrichment.

How it does this

• RepositorySearchTool now extends BaseTool and internally instantiates SDECodeSearchTool with mapped config.
• SDE result content is explicitly mapped to full_text in the minified response.
• Output model is now a plain Pydantic BaseModel to avoid framework-added _response payload noise.
• Repository metadata + reliability score are computed as before using existing utility functions.
• Tests now assert exact output keys and confirm removed fields are not present.

Files changed

• akd_ext/tools/code_search/repository_search.py
• tests/tools/code_search/test_repository_search.py

Testing

• Command:
  • uv run pytest tests/tools/code_search/test_repository_search.py -q
• Result:
  • 8 passed