Harden runtime and add backup foundation

src/atocore/projects/registry.py

@@ -3,6 +3,7 @@
 from __future__ import annotations
 
 import json
+import tempfile
 from dataclasses import asdict, dataclass
 from pathlib import Path
 
@@ -320,7 +321,15 @@ def _load_registry_payload(registry_path: Path) -> dict:
 
 def _write_registry_payload(registry_path: Path, payload: dict) -> None:
     registry_path.parent.mkdir(parents=True, exist_ok=True)
-    registry_path.write_text(
-        json.dumps(payload, indent=2, ensure_ascii=True) + "\n",
+    rendered = json.dumps(payload, indent=2, ensure_ascii=True) + "\n"
+    with tempfile.NamedTemporaryFile(
+        mode="w",
         encoding="utf-8",
-    )
+        dir=registry_path.parent,
+        prefix=f"{registry_path.stem}.",
+        suffix=".tmp",
+        delete=False,
+    ) as tmp_file:
+        tmp_file.write(rendered)
+        temp_path = Path(tmp_file.name)
+    temp_path.replace(registry_path)