TrimUI: dedicated OSD event watchdog and FN switch status synchronization

[leslieclemence]

Per request by @chrisj951 on #1681, this PR introduces a dedicated osd_sync_watchdog.sh for TrimUI OSD events rather than mixing OSD handlers into volume_sync_watchdog.sh.

Motivation & Background

On TrimUI devices with stock OSDD active (such as the Smart Pro and Smart Pro S), interactions in the Quick Menu / OSD (Cooler level, LED, Wi-Fi, Bluetooth, Rumble) drop event command files into /tmp/system/.
Furthermore, flipping the physical FN switch on the console executes scene-rgb-led.sh to turn LEDs on/off, but previously did not update the shared memory (shmvar ledswitch) or /tmp/trimui_osd/toggle_led/status, leaving the OSD tile out-of-sync with hardware.

Key Changes:

1. Dedicated osd_sync_watchdog.sh (spruce/scripts/osd_sync_watchdog.sh):
   • Watches /tmp/system/ using event-driven inotifywait (with an interval polling fallback).
   • Handles:
     • set_fanlevel / set_fan: calls apply_fan_level and save_fan_level.
     • led_turn_on / led_turn_off: controls RGB LEDs, removes/sets leds_forced_off flag, and syncs shmvar ledswitch & /tmp/trimui_osd/toggle_led/status.
     • wifi_turn_on / wifi_turn_off: controls wifi, updates SYSTEM_JSON, shmvar wifiswitch, and OSD status.
     • bluetooth_turn_on / bluetooth_turn_off: manages bluetooth daemon, updates SYSTEM_JSON, shmvar btswitch, and OSD status.
     • rumble_turn_on / rumble_turn_off: sets /sys/class/motor/max_scale, gives a tactile pulse, and syncs shmvar rumbleswitch & OSD status.
   • Leaves volume_sync_watchdog.sh 100% focused on ALSA volume.
2. Immediate OSD Status Sync on FN Switch:
   • spruce/scripts/FN_Button/scene-rgb-led.sh and fn-led-toggle.sh: Updates shmvar ledswitch and /tmp/trimui_osd/toggle_led/status on the very first lines, ensuring zero-latency UI status synchronization.
3. Isolated Launch in trimui_delegate.sh:
   • Launches osd_sync_watchdog.sh solely on TrimUI devices where /usr/trimui/osd/trimui_osdd is present.

Hardware Testing:

• Verified on TrimUI Smart Pro S:
  • Flipping FN switch immediately syncs OSD LED tile between ON and OFF.
  • Toggling Rumble in OSD immediately applies motor scale and gives a tactile confirmation pulse.
  • Toggling Fan, Wi-Fi, and Bluetooth in OSD properly applies hardware state and updates system configs.

[chrisj951]

You're missing the hooks in Saves/spruce/spruce-config.json