feat(voice): add iOS VAD runtime support

crates/chanora_audio/src/transmit_selector.rs

@@ -11,8 +11,7 @@
 //!   on PTT mode)
 //!
 //! Hard-mute is a final clamp; leaving the channel forces the gate
-//! to `false`. `VoiceActivity` is treated identically to
-//! `Continuous` per DEC-030 until a VAD implementation lands.
+//! to `false`. `VoiceActivity` is driven by Rust-owned VAD state.
 //!
 //! All four inputs are stored as atomics so any thread can update
 //! them without taking a lock. After each update we call
@@ -92,6 +91,7 @@ pub struct TransmitModeSelector {
     in_channel: AtomicBool,
     hard_mute: AtomicBool,
     ptt_held: AtomicBool,
+    voice_activity_open: AtomicBool,
     /// SDD-106 §5/§6 / SRS-209: latest resolved microphone
     /// permission state. Stored as a `u8` so writes from the
     /// JNI thread (Android permission requester → bridge) and
@@ -133,6 +133,7 @@ impl TransmitModeSelector {
             in_channel: AtomicBool::new(false),
             hard_mute: AtomicBool::new(false),
             ptt_held: AtomicBool::new(false),
+            voice_activity_open: AtomicBool::new(false),
             // SDD-106 §5: default to Granted on construction so
             // non-Android hosts (which never publish a permission
             // event) are not silently clamped. The Android bridge
@@ -226,6 +227,17 @@ impl TransmitModeSelector {
         self.ptt_held.load(Ordering::Relaxed)
     }
 
+    /// Rust-owned VAD gate input for VoiceActivity mode.
+    pub fn set_voice_activity_open(&self, v: bool) {
+        self.voice_activity_open.store(v, Ordering::Relaxed);
+        self.recompute();
+    }
+
+    /// Current Rust-owned VAD gate state.
+    pub fn voice_activity_open(&self) -> bool {
+        self.voice_activity_open.load(Ordering::Relaxed)
+    }
+
     /// Subscribe to `ptt_held` transitions. Used by the
     /// missed-key-up watchdog (SAD-079) so it fires on the actual
     /// PTT-key-down lifetime, not on the resolved `transmit_active`
@@ -265,8 +277,8 @@ impl TransmitModeSelector {
         }
         match self.mode() {
             TransmitMode::Ptt => self.ptt_held.load(Ordering::Relaxed),
-            // DEC-030: VoiceActivity behaves as Continuous in v1.
-            TransmitMode::Continuous | TransmitMode::VoiceActivity => true,
+            TransmitMode::Continuous => true,
+            TransmitMode::VoiceActivity => self.voice_activity_open.load(Ordering::Relaxed),
         }
     }
 
@@ -323,13 +335,17 @@ mod tests {
         assert!(g.load(), "continuous independent of key state");
     }
 
-    /// SWE4-UV-037: voice-activity mode matches continuous in v1.
+    /// SWE4-UV-037: voice-activity mode follows VAD state.
     #[test]
-    fn voice_activity_matches_continuous_v1() {
+    fn voice_activity_requires_vad_open() {
         let (g, s) = fresh();
         s.set_mode(TransmitMode::VoiceActivity);
         s.set_in_channel(true);
+        assert!(!g.load());
+        s.set_voice_activity_open(true);
         assert!(g.load());
+        s.set_voice_activity_open(false);
+        assert!(!g.load());
     }
 
     /// SWE4-UV-037 / SWE4-UV-041: hard-mute clamps the transmit