feat: add safe BLE discovery and network baseline tools

src/k1link/artifacts.py

@@ -0,0 +1,39 @@
+from __future__ import annotations
+
+import json
+import os
+import tempfile
+from datetime import UTC, datetime
+from pathlib import Path
+from typing import Any
+
+
+def utc_now_iso() -> str:
+    """Return a stable UTC timestamp for manifests and capture artifacts."""
+    return datetime.now(UTC).isoformat(timespec="milliseconds").replace("+00:00", "Z")
+
+
+def write_json_atomic(path: Path, payload: Any) -> None:
+    """Write JSON without exposing a partially written artifact."""
+    path = path.expanduser()
+    path.parent.mkdir(parents=True, exist_ok=True)
+    serialized = json.dumps(payload, ensure_ascii=False, indent=2) + "\n"
+
+    temp_name: str | None = None
+    try:
+        with tempfile.NamedTemporaryFile(
+            mode="w",
+            encoding="utf-8",
+            dir=path.parent,
+            prefix=f".{path.name}.",
+            suffix=".tmp",
+            delete=False,
+        ) as stream:
+            temp_name = stream.name
+            stream.write(serialized)
+            stream.flush()
+            os.fsync(stream.fileno())
+        Path(temp_name).replace(path)
+    finally:
+        if temp_name is not None:
+            Path(temp_name).unlink(missing_ok=True)