v26.5..18 AF/Slice Mute Button

[26.5.18] — 2026-05-26

Added

• New action: AF Mute. A dedicated one-press key for toggling
  RX audio mute on a slice. Defaults to slice A; configurable to
  B/C/D in the Property Inspector. The button face reflects the
  radio's actual mute state — synced from the audio_mute field
  in slice status frames — so changes made elsewhere (SmartSDR,
  AetherSDR, another button on the deck, a Smart Macro) are
  reflected here within milliseconds. Two states: blue speaker
  with sound waves for unmuted, red speaker with diagonal slash
  for muted. The default button label is "AF A" / "AF B" / etc.
  so it's clear at a glance which slice the button targets;
  override with a custom label in the PI if you'd rather name
  buttons "MAIN" and "SUB" or similar.
• The AF Volume action's existing mute behavior (dial press, touch
  tap, rotate-to-zero) is unchanged. AF Mute fills the gap when AF
  Volume is placed on a regular key — where pressing it jumps to a
  preset value instead of toggling mute.

Internal

• Brings the total action count to 32 (was 31).
• Uses the established slice-aware PI pattern (A/B/C/D dropdown
  defaulting to A) and the SettingsWatcher gate for
  onDidReceiveSettings so live re-configuration works correctly
  without spurious re-subscribes.