Add GitLab MCP Server tool configuration to agents via YAML and AI Catalog UI

Problem

GitLab's MCP Server tools are currently injected globally into all foundational agents when mcp_client is enabled, regardless of the agent's defined toolset, see #583935 (closed). In #583935 (closed), we'll make MCP tools available to agentic chat only.

Proposal

Let's add GitLab's MCP Server tool configuration to the agent catalog UI (https://gitlab.com/explore/ai-catalog/agents/), allowing users to assign MCP tools to agents—similar to how they currently add DAP tools. Provided that there are no

Open question:

• Should we re-use the existing dropdown to present all available tools (DAP + MCP) to the user?
• Will we need a new endpoint to provide available MCP tools?
• ...