Fix /docs: add explicit route for openapi.yaml

Flask static folder wasn't serving .yaml files automatically.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

aggregator.py

@@ -313,6 +313,12 @@ def index():
     return send_from_directory(ROOT_DIR, "index.html")
 
 
+@app.route("/openapi.yaml")
+def openapi_spec():
+    """Serve OpenAPI specification."""
+    return send_from_directory(ROOT_DIR, "openapi.yaml", mimetype="text/yaml")
+
+
 @app.route("/status", methods=["GET"])
 def get_status():
     """Return current status as JSON."""