feat(mcp-tool): wire McpToolService into deploy stack

Three pieces, all required for an end-to-end MCP tool call:

* McpToolService used generic spec names "request"/"response" instead of
  "mcp-tool-request"/"mcp-tool-response", so RequestResponseSpec's
  flow-config topic lookup never matched and consumers bound to literal
  subjects nobody else publishes to.

* Add entrypoints/mcp-tool.mjs (mirrors agent/librarian entrypoints) so
  the service can be launched in the prebuilt trustgraph-ts image.

* Add a `mcp-tool` service block to deploy/docker-compose.yml.

With these three fixes plus a `mcp-tool-request`/`mcp-tool-response`
entry in each flow's topics map, the agent ReAct loop can now invoke
remote MCP tools (verified end-to-end against Brave Search and FireCrawl).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ts/deploy/docker-compose.yml

@@ -298,6 +298,18 @@ services:
       - trustgraph
     restart: unless-stopped
 
+  mcp-tool:
+    image: trustgraph-ts:local
+    command: ["node", "entrypoints/mcp-tool.mjs"]
+    environment:
+      - NATS_URL=nats://nats:4222
+    depends_on:
+      nats:
+        condition: service_healthy
+    networks:
+      - trustgraph
+    restart: unless-stopped
+
   librarian:
     image: trustgraph-ts:local
     command: ["node", "entrypoints/librarian.mjs"]