feat(mcp): Bidirectional MCP Client Adapter (Dynamic Tool Discovery)

[sdageltc]

Summary & Motivation

letitloop currently includes a built-in MCP server (orchestrator/mcp_server.py), allowing external AI assistants (like Claude Desktop, Antigravity, Cursor, and Windsurf) to control letitloop as a macro-task engine.

The next evolution is Bidirectional MCP Support: enabling letitloop contracts to act as MCP clients that dynamically discover, mount, and execute tools provided by external MCP servers (e.g., PostgreSQL MCP, GitHub MCP, Puppeteer Browser MCP, Slack MCP).

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Proposed Architecture

1. MCPClientManager (orchestrator/mcp_client.py):
   • Manages stdio and SSE transport connections to external MCP servers declared in a .letitloop/mcp.json config.
   • Discovers available tools (tools/list) and translates them into tool definitions for worker adapters.
2. Contract Tool Binding:
   • Contracts can specify required_mcp_servers: ["postgres", "github"] in their contract metadata.
   • The worker adapter receives access only to the tools exposed by declared servers.

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Acceptance Criteria

• Can connect to standard stdio MCP servers using JSON-RPC 2.0.
• Passes discovered MCP tools to worker adapters.
• Isolates MCP server processes and terminates them cleanly on task completion.
• Tested with mock MCP servers in tests/test_mcp_client.py.