bdwidth: width only in PRINT_START

The CCD motion reading stays at 0 (actual_total_move:0), so motion mode
only produced false "Rounout" messages. ENABLE_WIDTH keeps the flow
compensation and the runout on a missing width; clogs and breaks are
left to AFC's buffer fault detection (filament_error_sensitivity).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CLAUDE.md

@@ -12,8 +12,10 @@ Voron 2.4 350, Klipper + Moonraker + Mainsail on a Raspberry Pi 4
 toolboard (USB), Leviathan mainboard as USB-CAN bridge, bd_pressure
 (load-check firmware, branch `load-check-extension` in
 `D:\Claude\bd_pressure-load-check\bd_pressure`), bdwidth (measures width and
-motion optically with a CCD; its motion reading is unreliable, so the purge
-check runs with `motion_check: False`), iHeater chamber heater.
+motion optically with a CCD; its motion reading stays at 0, so it runs width
+only (`ENABLE_WIDTH` in PRINT_START) and the purge check runs with
+`motion_check: False`; clogs and breaks are caught by AFC's buffer fault
+detection, `filament_error_sensitivity`), iHeater chamber heater.
 
 ## Working with the printer