docs: standardize skill-template and add development guide

scripts/util/timeutil.py

@@ -0,0 +1,20 @@
+"""时间戳与 ISO 展示。"""
+
+from __future__ import annotations
+
+import time
+from datetime import datetime
+from typing import Optional
+
+
+def now_unix() -> int:
+    return int(time.time())
+
+
+def unix_to_iso(ts: Optional[int]) -> Optional[str]:
+    if ts is None:
+        return None
+    try:
+        return datetime.fromtimestamp(int(ts)).isoformat(timespec="seconds")
+    except (ValueError, OSError, OverflowError):
+        return None