feat(bridge,core): add is_hard_muted and get_output_gain readback (TODO-037)

Add bridge read-back functions for hard-mute state and output gain.
Add core output_gain() getter. Document feature gaps in SRS.

core/chanora_core/src/lib.rs

@@ -1113,6 +1113,21 @@ impl ChanoraSession {
         Ok(())
     }
 
+    /// Read the current master output gain. Returns `1.0` (unity) if
+    /// audio is not started.
+    pub async fn output_gain(&self) -> f32 {
+        let guard = self.inner.lock().await;
+        let state = match guard.as_ref() {
+            Some(s) => s,
+            None => return 1.0,
+        };
+        let audio = match state.audio.as_ref() {
+            Some(a) => a,
+            None => return 1.0,
+        };
+        audio.output_gain()
+    }
+
     /// Set per-client output volume (SRS-075). `1.0` is unity, `0.0`
     /// mutes. No-op if audio is not started or client has no active
     /// voice queue.

crates/chanora_bridge/src/api.rs

@@ -837,6 +837,15 @@ pub async fn set_hard_mute(muted: bool) -> Result<(), BridgeError> {
     Ok(())
 }
 
+/// Read the current hard-mute state. Returns `true` when the audio
+/// engine is clamped and transmits nothing regardless of mode.
+pub async fn is_hard_muted() -> bool {
+    runtime()
+        .spawn(async { session().hard_mute() })
+        .await
+        .unwrap_or(false)
+}
+
 /// Coarse PTT input class (gen2 v0.9.3 / DEC-026). Stable strings;
 /// the bridge never carries raw key codes.
 #[derive(Debug, Clone, Copy)]
@@ -999,6 +1008,15 @@ pub async fn set_output_gain(gain: f32) -> Result<(), BridgeError> {
     Ok(())
 }
 
+/// Read the current master output gain. Returns `1.0` (unity) when
+/// audio is not started.
+pub async fn get_output_gain() -> f32 {
+    runtime()
+        .spawn(async { session().output_gain().await })
+        .await
+        .unwrap_or(1.0)
+}
+
 /// Set per-client output volume (SRS-075). `1.0` is unity, `0.0`
 /// mutes. No-op when client has no active voice queue. Volume is
 /// applied directly to the tsclientlib AudioQueue and takes effect
@@ -2394,7 +2412,7 @@ pub async fn enable_audio_debug_wav_dump(enabled: bool) -> Result<(), BridgeErro
         .spawn(async move { session().set_audio_debug_wav_dump(enabled).await })
         .await
         .map_err(|e| task_join_error("enable_audio_debug_wav_dump", e))?
-        .map_err(|e| BridgeError::Unmapped(format!("enable_audio_debug_wav_dump: {e}")))?;
+        .map_err(|e| BridgeError::unmapped_ctx("enable_audio_debug_wav_dump", e))?;
     Ok(())
 }