fix low level issues

bincio/edit/server.py

@@ -506,12 +506,7 @@ async def save_athlete(payload: dict[str, Any]) -> JSONResponse:
         encoding="utf-8",
     )
 
-    # Patch athlete.json in-place (preserves power_curve, updated_at, etc.)
-    data = json.loads(athlete_path.read_text(encoding="utf-8"))
-    data.update(overrides)
-    athlete_path.write_text(json.dumps(data, indent=2, ensure_ascii=False))
-
-    # Re-merge so _merged/athlete.json symlink stays valid
+    # Re-merge — merge_all() applies edits/athlete.yaml on top of athlete.json
     from bincio.render.merge import merge_all
     merge_all(dd)