feat(desktop): add message read-aloud playback

desktop/scripts/check-file-sizes.mjs

@@ -396,7 +396,10 @@ const overrides = new Map([
   // transition lock doc broadened to cover all protected-PID transitions, and
   // clear_agent_session_caches (per-pubkey retain) added alongside the
   // per-key clear. Load-bearing identity-contract change; queued to split.
-  ["src-tauri/src/app_state.rs", 1081],
+  // +4 (1081 -> 1085): message read-aloud experiment — the app-scoped
+  // MessageTtsState field (doc + init) added beside huddle_state. The state
+  // itself lives in message_tts.rs; only the wiring lands here.
+  ["src-tauri/src/app_state.rs", 1085],
   // multi-slot splitting + no-op suppression (#1309): the ReadStateManager
   // class grew from ~700 lines to ~1019 with the addition of
   // splitContextsIntoBudgetedSlots (pure fn + 5 tests), publishSplitSlots,

desktop/src-tauri/src/app_state.rs

@@ -48,6 +48,9 @@ pub struct AppState {
     pub channel_templates_store_lock: Mutex<()>,
     pub managed_agent_processes: Mutex<HashMap<ManagedAgentRuntimeKey, ManagedAgentPairRuntime>>,
     pub huddle_state: Mutex<HuddleState>,
+    /// App-scoped message read-aloud state (independent of huddle speech).
+    /// See `message_tts.rs` for the lifecycle contract.
+    pub message_tts: crate::message_tts::MessageTtsState,
     /// Tauri app handle — stored after setup so huddle commands can emit
     /// `huddle-state-changed` events without needing the handle threaded
     /// through every call site.
@@ -211,6 +214,7 @@ pub fn build_app_state() -> AppState {
         managed_agent_processes: Mutex::new(HashMap::new()),
         session_config_cache: Mutex::new(HashMap::new()),
         huddle_state: Mutex::new(HuddleState::default()),
+        message_tts: crate::message_tts::MessageTtsState::default(),
         app_handle: Mutex::new(None),
         audio_output_device: Mutex::new(None),
         media_proxy_port: AtomicU16::new(0),

desktop/src-tauri/src/huddle/mod.rs

@@ -197,6 +197,8 @@ pub async fn start_huddle(
         hs.phase = HuddlePhase::Creating;
         hs.parent_channel_id = Some(parent_channel_id.clone());
     }
+    // The huddle owns the audio device now — end any message read-aloud.
+    crate::message_tts::stop_message_playback(&state);
 
     let ephemeral_uuid = Uuid::new_v4();
     let ephemeral_channel_id = ephemeral_uuid.to_string();
@@ -357,6 +359,8 @@ pub async fn join_huddle(
         hs.parent_channel_id = Some(parent_channel_id.clone());
         hs.ephemeral_channel_id = Some(ephemeral_channel_id.clone());
     }
+    // The huddle owns the audio device now — end any message read-aloud.
+    crate::message_tts::stop_message_playback(&state);
 
     // Seed participant list with own pubkey as a fallback until relay responds.
     let own_pubkey = state

desktop/src-tauri/src/lib.rs

@@ -13,6 +13,7 @@ mod media_proxy;
 mod mesh_llm;
 #[cfg(not(feature = "mesh-llm"))]
 mod mesh_llm_stubs;
+mod message_tts;
 mod migration;
 #[cfg(test)]
 mod model_tests;
@@ -857,6 +858,8 @@ pub fn run() {
             get_model_status,
             set_tts_enabled,
             speak_agent_message,
+            message_tts::speak_chat_message,
+            message_tts::stop_chat_message_speech,
             add_agent_to_huddle,
             check_pipeline_hotstart,
             confirm_huddle_active,