add frontend process service

ai/shared.md

@@ -74,12 +74,15 @@ those changes with the most relevant parser, formatter, dry run, or check.
 - Run backend commands from `backend/`, or explicitly change into it in the
   command. The direnv target remains the worktree root.
 - Run frontend commands from `frontend/website/`.
-- `process-compose` does not start the frontend. Start it separately with
-  the worktree's assigned port when needed:
+- `process-compose` starts the frontend on the worktree's assigned port. To
+  start only the frontend:
 
   ```sh
   direnv exec "$(git rev-parse --show-toplevel)" \
-    npm run dev -- --port "$VITE_PORT"
+    npm run dev -- \
+    --host 127.0.0.1 \
+    --port "$VITE_PORT" \
+    --strictPort
   ```
 
 - When a normally valid check fails because a required service is down,