Closes the mobile parity push.
- MobileVoiceJoinSheet: full pre-join camera preview. Dormant-by-default (never auto-fires getUserMedia), explicit user gesture to arm, hard-bound disarm on sheet close (any path). Camera picker popup portaled to document.body so a long device list stays scrollable above the aspect-video preview tile (max-height min(50vh,320px), iOS scroll momentum). iOS Safari-safe: autoPlay playsInline muted + post-await play().
- MobileSettingsScreen: Keybinds + Desktop sections gated on isElectron(); they reuse the existing KeybindsPanel/DesktopPanel which are already mobile-fit. screenMap entries added in MobileShell. (Verify on Electron desktop build at narrow viewport.)
- ToastContainer: real overlap was hiding the voice-fullscreen control bar. Mobile branch now reads isMobile/mobileStack/currentVoiceChannelId and computes the bottom offset across five mobile states (voice-full / pushed+voice / pushed / root+voice / root), all with safe-area-inset-bottom; left-3 right-3 + items-center keeps toasts in the safe-tap zone. Desktop bottom-6 right-6 unchanged.
Specs: docs/systems/mobile-ui.md (Toast Positioning section, screenMap rows, Electron-entry rationale, z-index row); docs/systems/voice.md (Mobile pre-join preview subsection covering lifecycle + camera picker portal).
Jannis Braun