Re-add MCP bridge so Hermes can delegate to the real Claude Code CLI

Recreates the PR #17 change (closed without merging, then asked for back
after confirming a real ANTHROPIC_API_KEY would mean separate/duplicate
billing rather than actually using the Pro/Max subscription).

New POST /mcp endpoint (Streamable HTTP transport, stateless — fresh
McpServer+transport per request) exposing one tool, ask_claude_code: runs
the real `claude` binary against a prompt, billed against the subscription
rather than API credits. Works specifically because it's the actual CLI
making the request server-side. Read-only — no Edit/Write/git-push/
git-commit tools.

Also removes litellm-config.yaml's "anthropic-claude" model entry: it only
ever worked when the real claude CLI itself was the caller (proven earlier),
so having it listed as a selectable model was actively misleading — Hermes
picking it directly is exactly what produced the '401: Missing Anthropic
API Key' confusion that led back to this bridge. The MCP tool is the actual
working path now; general_settings.forward_client_headers_to_llm_api is
also removed since nothing uses it anymore.

Tested end-to-end locally again before pushing (built the image, ran it,
full MCP handshake via curl) — real 'pong' from the real claude CLI.

docker-compose.yml

@@ -120,9 +120,10 @@ services:
       - "traefik.http.services.hermes-dashboard.loadbalancer.server.port=9119"
 
   claude-agent:
-    # Gitea PR-review only now — no Matrix presence (see hermes above; only one agent
-    # is meant to be in Matrix). Still triggered by Gitea's pull_request webhook and
-    # posts review comments there, entirely independent of Matrix/LiteLLM.
+    # No Matrix presence (see hermes above; only one agent is meant to be in Matrix).
+    # Two things call this now: Gitea's pull_request webhook (PR review), and Hermes,
+    # over MCP (POST /mcp), to delegate a question to the real `claude` CLI when it
+    # specifically wants the Claude subscription instead of whatever LiteLLM routed it to.
     image: ${GITEA_REGISTRY_IMAGE}
     container_name: claude-agent
     restart: unless-stopped
@@ -136,6 +137,9 @@ services:
       # Claude subscription (Pro/Max) auth via `claude setup-token`, not API billing —
       # Claude Code reads this in preference to ANTHROPIC_API_KEY when both could apply.
       CLAUDE_CODE_OAUTH_TOKEN: ${CLAUDE_CODE_OAUTH_TOKEN}
+      # Shared secret for the /mcp bridge endpoint (internal network only either way, but
+      # this keeps it from being callable by anything that merely reaches the container).
+      MCP_BRIDGE_KEY: ${MCP_BRIDGE_KEY}
     volumes:
       - agent_workspace:/workspace
     networks: