perf(web): deduplicate control plane gate state

my-tools/watch_blender_web_scheduler.py

@@ -32,6 +32,14 @@ def now() -> str:
 
 def write_json(path: Path, value: dict) -> None:
     path.parent.mkdir(parents=True, exist_ok=True)
+    try:
+        current = json.loads(path.read_text(encoding="utf-8"))
+        stable_current = {key: item for key, item in current.items() if key != "updatedAt"}
+        stable_next = {key: item for key, item in value.items() if key != "updatedAt"}
+        if stable_current == stable_next:
+            return
+    except (OSError, json.JSONDecodeError):
+        pass
     temporary = path.with_suffix(path.suffix + f".tmp-{os.getpid()}")
     temporary.write_text(json.dumps(value, ensure_ascii=False, indent=2) + "\n", encoding="utf-8")
     temporary.replace(path)