Expose API complexity metadata in MCP tool results

[omribz156]

Closes #242.

Summary

• Adds a small MCP-side complexity tracker around monday API requests made during tool execution.
• Auto-adds the root complexity { query before after reset_in_x_seconds } selection when a tool query/mutation does not already request it.
• Returns the latest complexity value through MCP _meta.complexity, and includes _meta.complexities when a tool makes multiple API calls.
• Keeps existing tool payloads stable by removing only the auto-injected complexity field from structuredContent.
• Preserves existing tool-provided metadata in MCP-formatted responses.

Verification

• jest -c jest.config.ts --runTestsByPath C:\projects\oss-supporter\codex\slices\durable\mondaycom-mcp\2026-05-21-complexity-metadata\repo\packages\agent-toolkit\src\mcp\toolkit.test.ts --runInBand
• prettier --check packages/agent-toolkit/src/mcp/toolkit.ts packages/agent-toolkit/src/mcp/toolkit.test.ts --ignore-path .prettierignore
• eslint packages/agent-toolkit/src/mcp/toolkit.ts packages/agent-toolkit/src/mcp/toolkit.test.ts --ignore-path .eslintignore
• git diff --check

Notes: I also tried yarn workspace @mondaydotcomorg/agent-toolkit build, but this local reused-dependency setup is missing @rollup/plugin-typescript. A full tsc -p packages/agent-toolkit/tsconfig.json --noEmit also still hits the existing deep type-instantiation error in src/openai/toolkit.ts.

This was implemented with Codex assistance, with the patch kept focused and manually reviewed before sending.