Sync Brick Fn actions and the volume keys with spruce state

[Felixmil]

The TrimUI Brick "Fn Key and Switch Settings" actions are stock scripts that write to firmware sinks spruce does not use, so their effects did not stay in sync with spruce's own state. This reworks three of those actions to go through spruce's own helpers, so the hardware, the stored value, and the in-UI sliders all move together. It also stops the audio actions from triggering the stock volume popup, which was redundant with the switch's own on-screen toast, and adds a watcher so the in-UI volume bar follows the physical volume keys.

Backlight action

The "LCD brightness switcher" action wrote the new level to /tmp/system/set_brightness for the stock hardwareservice to apply, which spruce does not consume, so the brightness slider and stored value did not follow the key. It now sources helperFunctions.sh and cycles the backlight with spruce's current_backlight / set_backlight, stepping through 1, 4, 7, 10 and wrapping back to 1. Because set_backlight records the value spruce reads elsewhere, the UI slider updates in step.

Silent Mode action

Silent Mode hard-muted the speaker via /sys/class/speaker/mute but never told spruce, so the in-UI volume value stayed at its old level while muted. It now also drops the volume to 0 through spruce's set_volume on enter (so the volume value reflects the mute) and restores the prior volume on exit. The speaker hard-mute is kept as a backstop.

Quiet Mode action

Quiet Mode poked an ALSA mixer control directly (tinymix set 9 N), which spruce neither reads nor respects, so nothing audible changed and the volume slider stayed wrong. It now lowers the volume to a low but audible level through spruce's set_volume on enter, saving the current volume first, and restores that saved volume on exit, mirroring the Silent Mode approach.

Volume popup suppression

In game (when MainUI is not running) set_volume shows the stock volume OSD popup. When Silent or Quiet was toggled by the switch this popped up alongside the switch's own toast, which was redundant. set_volume gains an optional third argument that controls the popup (defaulting to shown, so every existing caller is unchanged), and the Silent and Quiet actions opt out of it. The physical volume keys still show their popup as before.

Volume key sync

The physical Volume +/- keys are handled entirely by the stock firmware, which adjusts the audio and writes the new level to /tmp/system/set_volume on every key event (autorepeat included). spruce never read that file back, so its stored volume (.vol) only changed when spruce itself set the volume. Since the in-UI volume bar reads .vol, holding a volume key moved the audio but the bar updated once at most and never ramped. A small watchdog (spruce/brick/volume_sync_watchdog.sh) now polls /tmp/system/set_volume and mirrors the value into spruce's volume through set_volume (config only, with the popup suppressed because the firmware already draws its own), so the bar tracks the hardware keys including while held. It is started from device_init_a133p and stopped on shutdown alongside the other watchdogs.

Notes

These changes are independent of the daemon that dispatches Fn key presses (see #1548, which starts keymon); they only change what the actions do when they run. The Fn key and switch actions in this PR only reach users once keymon is also started, but the volume key sync is independent of keymon and works on its own. The volume sync watcher is launched next to the line #1548 adds to device_init_a133p, so merging the two produces a one-line conflict that is resolved by keeping both lines. #1550 edits a different part of the same file (the runtime mounts) and merges independently.

Validated on a physical Brick (FW 1.1.1): the backlight cycle runs 1 → 4 → 7 → 10 → 1 with the stored value updating each step, Silent Mode drops the volume value to 0 on enter and restores the previous level on exit, Quiet Mode drops the volume to a low level on enter and restores the previous level on exit, in game the switch no longer shows the stock volume popup for Silent or Quiet while the volume keys still do, and holding the Volume +/- keys now ramps the in-UI volume bar smoothly in sync with the audio.