Fix session processing state leaking across session switches

Root cause:
- Processing ownership was derived from UI view state in ChatInterface.
- While switching sessions, an in-flight isLoading=true could stamp the newly selected session as processing, even if a different session was actually running.
- session-status handling only promoted isProcessing=true and did not clear stale processing state on isProcessing=false, which could leave sessions blocked.
Changes:
- ChatInterface: removed implicit processing propagation effect that called onSessionProcessing(selectedSession?.id || currentSessionId) when isLoading was true.
  This decouples processing ownership from transient view/session transitions.
- useChatComposerState: added onSessionProcessing callback usage and explicitly marks processing at submit time for the concrete effectiveSessionId (non-temporary IDs only).
  This ties processing to the session that actually started work.
- useChatRealtimeHandlers: expanded session-status handling to support both states.
  - isProcessing=true: mark session as processing; set loading/abort only when it is the currently viewed session.
  - isProcessing=false: clear active+processing markers and clear loading indicators for the current session view.
Behavioral outcome:
- Running session A no longer blocks session B after navigation.
- Users can work in multiple sessions concurrently, and processing badges/loading state stay session-scoped.
Verification:
- npm run typecheck
- npm run build

src/components/chat/hooks/useChatComposerState.ts

@@ -47,6 +47,7 @@ interface UseChatComposerStateArgs {
   sendMessage: (message: unknown) => void;
   sendByCtrlEnter?: boolean;
   onSessionActive?: (sessionId?: string | null) => void;
+  onSessionProcessing?: (sessionId?: string | null) => void;
   onInputFocusChange?: (focused: boolean) => void;
   onFileOpen?: (filePath: string, diffInfo?: unknown) => void;
   onShowSettings?: () => void;
@@ -98,6 +99,7 @@ export function useChatComposerState({
   sendMessage,
   sendByCtrlEnter,
   onSessionActive,
+  onSessionProcessing,
   onInputFocusChange,
   onFileOpen,
   onShowSettings,
@@ -569,6 +571,9 @@ export function useChatComposerState({
         pendingViewSessionRef.current = { sessionId: null, startedAt: Date.now() };
       }
       onSessionActive?.(sessionToActivate);
+      if (effectiveSessionId && !isTemporarySessionId(effectiveSessionId)) {
+        onSessionProcessing?.(effectiveSessionId);
+      }
 
       const getToolsSettings = () => {
         try {
@@ -666,6 +671,7 @@ export function useChatComposerState({
       executeCommand,
       isLoading,
       onSessionActive,
+      onSessionProcessing,
       pendingViewSessionRef,
       permissionMode,
       provider,

src/components/chat/hooks/useChatRealtimeHandlers.ts

@@ -956,12 +956,26 @@ export function useChatRealtimeHandlers({
 
       case 'session-status': {
         const statusSessionId = latestMessage.sessionId;
+        if (!statusSessionId) {
+          break;
+        }
+
         const isCurrentSession =
           statusSessionId === currentSessionId || (selectedSession && statusSessionId === selectedSession.id);
-        if (isCurrentSession && latestMessage.isProcessing) {
-          setIsLoading(true);
-          setCanAbortSession(true);
+
+        if (latestMessage.isProcessing) {
           onSessionProcessing?.(statusSessionId);
+          if (isCurrentSession) {
+            setIsLoading(true);
+            setCanAbortSession(true);
+          }
+          break;
+        }
+
+        onSessionInactive?.(statusSessionId);
+        onSessionNotProcessing?.(statusSessionId);
+        if (isCurrentSession) {
+          clearLoadingIndicators();
         }
         break;
       }

src/components/chat/view/ChatInterface.tsx

@@ -180,6 +180,7 @@ function ChatInterface({
     sendMessage,
     sendByCtrlEnter,
     onSessionActive,
+    onSessionProcessing,
     onInputFocusChange,
     onFileOpen,
     onShowSettings,
@@ -238,13 +239,6 @@ function ChatInterface({
     };
   }, [canAbortSession, handleAbortSession, isLoading]);
 
-  useEffect(() => {
-    const processingSessionId = selectedSession?.id || currentSessionId;
-    if (processingSessionId && isLoading && onSessionProcessing) {
-      onSessionProcessing(processingSessionId);
-    }
-  }, [currentSessionId, isLoading, onSessionProcessing, selectedSession?.id]);
-
   useEffect(() => {
     return () => {
       resetStreamingState();