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.

agent/package.json

@@ -8,6 +8,8 @@
     "start": "node src/server.js"
   },
   "dependencies": {
-    "express": "^4.19.2"
+    "express": "^4.19.2",
+    "@modelcontextprotocol/sdk": "^1.30.0",
+    "zod": "^3.23.8"
   }
 }