Add support for retrieving artist URLs via the MCP agent.\n\n- Implement the agents.ArtistURLRetriever interface.\n- Add the GetArtistURL method, which calls the 'get_artist_url'\n tool on the external MCP server.\n- Define the necessary constants and argument struct.\n\nThis mirrors the existing implementation for GetArtistBiography, reusing\nthe persistent process and client logic.
Modify the MCPAgent to automatically attempt restarting the external\nserver process if it detects the process has exited.\n\n- Replaced sync.Once with mutex-protected checks (a.client == nil) to allow\n re-initialization.\n- The monitoring goroutine now cleans up agent state (nils client, cmd, stdin)\n upon process exit, signaling the need for restart.\n- ensureClientInitialized now attempts to start/initialize if the client is nil.\n- GetArtistBiography checks client validity again after locking to handle race\n conditions where the process might die just after initialization check.
Refactor MCPAgent to maintain a persistent external server process.\n\nInstead of starting and stopping the MCP server for each request, the agent\nnow uses sync.Once for lazy initialization on the first call.\nIt stores the running exec.Cmd, stdio pipes, and the mcp.Client\nin the agent struct.\n\nA sync.Mutex protects concurrent access to the client/pipes.\nA goroutine monitors the process using cmd.Wait() and logs if it exits\nunexpectedly.\n\nThis avoids the overhead of process creation/destruction on every\nmetadata retrieval request.
Add a new agent implementation MCPAgent in core/agents/mcp.\n\nThis agent interacts with an external Model Context Protocol (MCP) server\nusing the github.com/metoro-io/mcp-golang library via stdio.\n\nIt currently implements the ArtistBiographyRetriever interface to fetch\nbiographies by calling the 'get_artist_biography' tool on the MCP server.\nThe path to the MCP server executable is hardcoded for this PoC.\n\nIncludes basic Ginkgo test setup for the new agent.
