data_model: split windows out of doors into own domain

- Add extract_windows() and register 'windows' in ALL_DOMAINS
- Remove windows extraction from extract_doors; no more double keys
- extract_windows also captures the overall windows.open_state

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

server/data_model.py

@@ -198,7 +198,15 @@ def extract_doors(vehicle) -> dict | None:
     except Exception:
         log.debug("vehicle.doors unavailable", exc_info=True)
 
+    return result or None
+
+
+def extract_windows(vehicle) -> dict | None:
+    result: dict = {}
+
     try:
+        if vehicle.windows.open_state.value is not None:
+            result["open_state"] = _str(vehicle.windows.open_state)
         window_entries = {}
         for name, win in vehicle.windows.windows.items():
             if win.open_state.value is not None:
@@ -219,6 +227,7 @@ ALL_DOMAINS: dict[str, Callable] = {
     "vehicle": extract_vehicle,
     "position": extract_position,
     "doors": extract_doors,
+    "windows": extract_windows,
 }