Reduce Linux setup ambiguity and surface desktop input/message failures honestly

Clarify ONNX Runtime guidance with direct-open install hints, restore desktop WebRTC VAD visibility, map mouse side buttons through focused PTT capture/runtime paths, and wait for server acks before showing chat sends as successful.

Constraint: Linux release UX must stay functional when ONNX Runtime is optional and GNOME portal availability varies
Rejected: Keep desktop VAD locked to Silero only | misleads users when ONNX Runtime is skipped
Confidence: medium
Scope-risk: moderate
Directive: Preserve the protocol send-ack wait path for chat so UI success always tracks real server acceptance
Tested: flutter analyze lib/main.dart lib/widgets/chat_views.dart lib/widgets/input_dialogs.dart lib/widgets/startup_dependency_screen.dart; flutter test test/widgets/input_dialogs_test.dart test/widgets/chat_views_test.dart test/services/startup_dependency_check_test.dart test/widgets/startup_dependency_screen_test.dart test/widgets/voice_settings_controls_test.dart test/widgets/audio_processing_config_state_test.dart; cargo test -p chanora_protocol --lib; cargo test -p chanora_audio ptt_backends --lib
Not-tested: Live manual GNOME portal rebind/global PTT on a real desktop session; observer-bot chat against a live server after the sender-name fallback change

crates/chanora_audio/src/ptt_backends/linux.rs

@@ -105,7 +105,7 @@ fn is_gnome_on_wayland() -> bool {
 trait BlockingGlobalShortcuts {
     /// Version property (read on the blocking proxy as a fast
     /// reachability probe).
-    #[zbus(property)]
+    #[zbus(property, name = "version")]
     fn version(&self) -> zbus::Result<u32>;
 }