Implement Tool Search Tool

[bhb]

Describe the feature or problem you’d like to solve

Implement Tool Search Tool as described by Anthopropic here.

Proposed solution

By adding defer_loading: true to most tools, the context required by the GitHub MCP server would dramatically shrink. On our team, we already limit tools to a minimal set using GITHUB_TOOLSETS but even so, the tool definitions take up 11.1% of my context on a fresh instance of Claude Code.