[DO NOT MERGE until gitagent#59] docs(gitagent): add MCP Client page to /docs

[Nivesh353]

⛔️ Blocked — do not merge yet.
This documents the MCP client feature, which ships in
open-gitagent/gitagent#59. Merge this only after that PR is merged
and the feature is released. Kept as a draft until then.

(If #59 is already merged & released, this note and the draft state can be
removed — the docs are then safe to merge immediately.)

Depends on: open-gitagent/gitagent#59

What this adds

A new MCP Client page under /docs/mcp (Capabilities group), documenting
GitAgent as an MCP client:

• Configuring servers via agent.yaml and the SDK (mcpServers)
• Runtime tool discovery, server__tool namespacing/sanitization, result flattening
• Fail-soft behavior and lazy loading of the MCP SDK
• Filesystem-server try-it-yourself walkthrough + troubleshooting checklist

Files

• src/components/gitAgent/GitAgentMCP.tsx (new)
• src/components/gitAgent/GitAgentSidebar.tsx — sidebar entry
• src/pages/GitAgentDocsPage.tsx — route registration

Merge checklist

• Feat/mcp client support gitagent#59 merged & released
• Mark this PR "Ready for review"

[vercel]

@Nivesh353 is attempting to deploy a commit to the shreyas-lyzr's projects Team on Vercel.

A member of the Team first needs to authorize it.