Add an MCP server for the API, deployable next to the application

mcp/ exposes both APIs as MCP tools, one per operation in openapi.yaml,
named after the Laravel route each lands on (public_projects_index,
admin_pages_update, ...). Nothing is written by hand: the tools are
derived from the document the target application serves, which the
contract tests already hold to the truth.

Two transports over one core:

- stdio (`node mcp/server.mjs`), registered in .mcp.json, signing in
  with credentials from the environment and refreshing the token.
- Streamable HTTP (`--http`), stateless, deployed as the landing-mcp
  service. It holds no credentials: each request brings its caller's
  Pireon Basic credentials or bearer token, so the API applies that
  person's permissions. Sessions live in memory keyed by a hash,
  refused credentials are remembered for a minute, and the spec is
  reloaded every minute so new endpoints appear without a redeploy.

Left out on purpose: the token exchange, telemetry, and the contact and
apply forms, which notify real people. The preview secret is never sent
for anonymous callers, and is unset in the deployment by default.

A CI job runs the Node tests, including the HTTP mode end to end
against a fake application.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

.github/workflows/tests.yml

@@ -79,3 +79,24 @@ jobs:
       - uses: actions/checkout@v4
 
       - run: docker compose -f docker-compose.test.yml run --rm test
+
+  # The MCP server derives its tools from openapi.yaml, so a change to the
+  # document can break it without touching a line under mcp/ — two operations
+  # that map to the same tool name, say. Cheap enough to run on every push.
+  mcp:
+    runs-on: ubuntu-latest
+    defaults:
+      run:
+        working-directory: mcp
+    steps:
+      - uses: actions/checkout@v4
+
+      - uses: actions/setup-node@v4
+        with:
+          node-version: 22
+          cache: npm
+          cache-dependency-path: mcp/package-lock.json
+
+      - run: npm ci
+
+      - run: npm test