feat: serve the MCP server at /mcp on the local servers

Mount the local MCP server at /mcp on the development and preview
servers for clients that connect by URL. The route accepts only
requests from this machine that name a loopback host and, when an
Origin is sent, come from a loopback origin, and drains oversized
bodies so the 413 response is delivered. The provider-order regression
test now pins the route between the providers and the API fallback.

scripts/format-scope.json

@@ -878,5 +878,6 @@
   "src/tools/queries/mobility.test.mjs",
   "src/tools/queries/environment.test.mjs",
   "src/tools/queries/maritime.test.mjs",
-  "src/tools/queries/share.test.mjs"
+  "src/tools/queries/share.test.mjs",
+  "src/tools/localRoute.test.mjs"
 ]