Remove _is_completely_open property and init _state with None

- We init `_state` with None and let the `_determine_cover_state` function populate the value from current positions
- Ensures all lines are coverable by tests

Author: jeverley

zha/application/platforms/cover/__init__.py

@@ -103,7 +103,7 @@ def __init__(
         self._lift_transition_timer: asyncio.TimerHandle | None = None
         self._tilt_transition_timer: asyncio.TimerHandle | None = None
 
-        self._state: CoverState | None = CoverState.OPEN
+        self._state: CoverState | None = None
         self._determine_cover_state(refresh=True)
 
     def recompute_capabilities(self) -> None:
@@ -163,7 +163,12 @@ def restore_external_state_attributes(
             return
         if state == CoverState.CLOSING and self.is_closed:
             return
-        if state == CoverState.OPENING and self._is_completely_open:
+        if (
+            state == CoverState.OPENING
+            and self._state == CoverState.OPEN
+            and self.current_cover_position in (100, None)
+            and self.current_cover_tilt_position in (100, None)
+        ):
             return
 
         self._state = state
@@ -244,17 +249,6 @@ def _previous_cover_tilt_position(self) -> int | None:
         """Return the previous tilt position of ZHA cover."""
         return self._tilt_position_history[0]
 
-    @property
-    def _is_completely_open(self) -> bool | None:
-        """Return True if the cover is completely open."""
-        if not self._state:
-            return None
-        return (
-            self._state == CoverState.OPEN
-            and self.current_cover_position in (100, None)
-            and self.current_cover_tilt_position in (100, None)
-        )
-
     @staticmethod
     def _determine_state(
         current: int | None,