Add MCP bridge to claude-agent so Hermes can delegate to the real Claude Code CLI

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 Pro/Max
subscription rather than API credits. This works specifically because it's
the actual claude CLI making the request server-side — the same reason
Hermes itself can't authenticate with the subscription directly (proven
earlier: Anthropic rejects the OAuth token from any client that isn't the
real CLI's exact request fingerprint). Read-only: no Edit/Write/git-push/
git-commit tools, since this is a quick-answer bridge, not a repo editor.

Tested end-to-end locally (built + ran the image, curled the full MCP
handshake: initialize -> tools/list -> tools/call) before pushing — got a
real 'pong' back from the actual claude CLI through the MCP protocol.

To register it with Hermes (lives in its own data volume, not git — see
.env.example comment):
  docker exec hermes hermes config set mcp_servers.claude-code.url http://claude-agent:3001/mcp
  docker exec hermes hermes config set 'mcp_servers.claude-code.headers.Authorization' 'Bearer <MCP_BRIDGE_KEY>'

.env.example

@@ -21,6 +21,12 @@ GITEA_REGISTRY_IMAGE=gitea.apps.williamturner.eu/<your-gitea-username>/<repo-nam
 # Run `claude setup-token` interactively (needs a browser + Claude Pro/Max subscription)
 # to generate this — it's a long-lived OAuth token, not an API key.
 CLAUDE_CODE_OAUTH_TOKEN=
+# Any random string — shared secret for claude-agent's /mcp bridge endpoint (see
+# agent/src/mcpBridge.js), which lets Hermes delegate a question to the real `claude`
+# CLI (billed against the subscription above) via MCP. Register it in Hermes with:
+#   docker exec hermes hermes config set mcp_servers.claude-code.url http://claude-agent:3001/mcp
+#   docker exec hermes hermes config set 'mcp_servers.claude-code.headers.Authorization' 'Bearer <this value>'
+MCP_BRIDGE_KEY=
 
 # --- litellm (local LLM gateway — used by Hermes, see litellm-config.yaml) ---
 OPENROUTER_API_KEY=