Update Protocol Engine to only change hardware state only if the tip …

…drop succeeds.

This is, finally, the part that makes the actual behavioral change and fixes the actual bug.

Having split up drop_tip(), we can now do the hardware API's state updates only after we've verified that the tip drop has physically  succeeded. This mirrors what Protocol Engine does for its own state after tip drop errors--see TipPhysicallyAttachedError.

api/src/opentrons/protocol_engine/execution/tip_handler.py

@@ -238,6 +238,7 @@ async def pick_up_tip(
         await self._hardware_api.tip_pickup_moves(
             mount=hw_mount, presses=None, increment=None
         )
+        # Allow TipNotAttachedError to propagate.
         await self.verify_tip_presence(pipette_id, TipPresenceStatus.PRESENT)
 
         self._hardware_api.cache_tip(hw_mount, actual_tip_length)
@@ -248,6 +249,9 @@ async def pick_up_tip(
             tiprack_diameter=nominal_tip_geometry.diameter,
         )
 
+        # todo(mm, 2024-10-15): The hardware API's original pick_up_tip() implementation
+        # seems to set the *current* volume to 0, not the working volume.
+        # Investigate that discrepancy.
         self._hardware_api.set_working_volume(
             mount=hw_mount,
             tip_volume=nominal_tip_geometry.volume,
@@ -270,9 +274,14 @@ async def drop_tip(self, pipette_id: str, home_after: Optional[bool]) -> None:
         else:
             kwargs = {}
 
-        await self._hardware_api.drop_tip(mount=hw_mount, **kwargs)
+        await self._hardware_api.drop_tip_moves(mount=hw_mount, **kwargs)
+
+        # Allow TipNotAttachedError to propagate.
         await self.verify_tip_presence(pipette_id, TipPresenceStatus.ABSENT)
 
+        await self._hardware_api.remove_tip(hw_mount)
+        self._hardware_api.set_current_tiprack_diameter(hw_mount, 0)
+
     async def add_tip(self, pipette_id: str, tip: TipGeometry) -> None:
         """See documentation on abstract base class."""
         hw_mount = self._state_view.pipettes.get_mount(pipette_id).to_hw_mount()