* feat(mcp): restrict grep_app tools to librarian agent only
Reduces token usage by disabling grep_app MCP tools globally and enabling them only for the librarian agent, which uses them for GitHub code search during documentation lookups.
Changes:
- Add grep_app_* tool disable globally in config.tools
- Add grep_app_* tool enable for librarian agent
- Remove grep_app references from explore agent prompt (no access)
Closes#394
* chore: changes by sisyphus-dev-ai
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Co-authored-by: sisyphus-dev-ai <sisyphus-dev-ai@users.noreply.github.com>