Tab cycles focus to sidebar where Up/Down navigates channels
and Enter joins the selected one. Muted/deafened users show
status symbols in the channel tree.
Textual does not expose key-release events, so KittyPtt
hold-mode never received key_up and stayed transmitting.
Auto-detect now tries evdev first, then falls back to
toggle (press-on/press-off). Default mode changed to toggle.