fix(filter-wheel): reset all W/W2 homing-phase flags at HOME entry

A HOME command is dispatched even while a previous home is in progress
(process_serial_message does not gate on mcu_cmd_execution_in_progress).
Clearing only is_backing_off_W left a stale is_homing_W, so check_homing_w()
could run alongside the new back-off phase and read a stale latch — the very
failure this branch fixes. Reset is_homing_W(2) and is_preparing_for_homing_W(2)
too, so a new home always starts the back_off -> prepare -> check sequence clean.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: Alpaca233

firmware/controller/src/commands/stage_commands.cpp

@@ -673,7 +673,14 @@ void callback_home_or_zero()
             tmc4361A_disableVirtualLimitSwitch(&tmc4361[w], -1);
             tmc4361A_disableVirtualLimitSwitch(&tmc4361[w], 1);
             homing_direction_W = buffer_rx[3];
+            // Clear every W homing-phase flag so a new HOME starts the
+            // back_off -> prepare -> check sequence from a clean state, even if
+            // a prior W home was still in progress (commands are accepted while
+            // mcu_cmd_execution_in_progress). Otherwise a stale is_homing_W lets
+            // check_homing_w() run concurrently and read a stale latch.
             home_W_found = false;
+            is_homing_W = false;
+            is_preparing_for_homing_W = false;
             is_backing_off_W = false;
             if (homing_direction_W == HOME_NEGATIVE) // use the left limit switch for homing
             {
@@ -718,7 +725,11 @@ void callback_home_or_zero()
             tmc4361A_disableVirtualLimitSwitch(&tmc4361[w2], -1);
             tmc4361A_disableVirtualLimitSwitch(&tmc4361[w2], 1);
             homing_direction_W2 = buffer_rx[3];
+            // Clear every W2 homing-phase flag for a clean state-machine start
+            // (see the AXIS_W comment above).
             home_W2_found = false;
+            is_homing_W2 = false;
+            is_preparing_for_homing_W2 = false;
             is_backing_off_W2 = false;
             if (homing_direction_W2 == HOME_NEGATIVE) // use the left limit switch for homing
             {