Phase 3: closing-overlay fix + goodbye-composer dedupe

Customer chat refreshSessionStatus now clears sessionExpired carryover so the
goodbye composer renders correctly when re-opening a closing session from
history. Backend /api/shared/chat/:id/info returns goodbye_submitted_by_me;
both apps suppress the composer for the side that has already submitted and
render an awaiting-banner view instead.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

client_app/lib/core/chat/chat_notifier.dart

@@ -30,6 +30,7 @@ class ChatConnectedData extends ChatData {
   final bool sessionExpired;
   final bool sessionPaused;
   final bool sessionClosing;
+  final bool goodbyeSubmitted;
   final Map<String, dynamic>? extensionResponse;
 
   const ChatConnectedData({
@@ -39,6 +40,7 @@ class ChatConnectedData extends ChatData {
     this.sessionExpired = false,
     this.sessionPaused = false,
     this.sessionClosing = false,
+    this.goodbyeSubmitted = false,
     this.extensionResponse,
   });
 
@@ -49,6 +51,7 @@ class ChatConnectedData extends ChatData {
     bool? sessionExpired,
     bool? sessionPaused,
     bool? sessionClosing,
+    bool? goodbyeSubmitted,
     Map<String, dynamic>? extensionResponse,
   }) {
     return ChatConnectedData(
@@ -58,6 +61,7 @@ class ChatConnectedData extends ChatData {
       sessionExpired: sessionExpired ?? this.sessionExpired,
       sessionPaused: sessionPaused ?? this.sessionPaused,
       sessionClosing: sessionClosing ?? this.sessionClosing,
+      goodbyeSubmitted: goodbyeSubmitted ?? this.goodbyeSubmitted,
       extensionResponse: extensionResponse ?? this.extensionResponse,
     );
   }
@@ -150,8 +154,12 @@ class Chat extends _$Chat {
         state = current.copyWith(sessionExpired: true);
         return;
       }
+      final goodbyeSubmittedByMe = data?['goodbye_submitted_by_me'] as bool? ?? false;
       state = current.copyWith(
         sessionClosing: status == SessionStatus.closing,
+        sessionPaused: status == SessionStatus.extending,
+        sessionExpired: false,
+        goodbyeSubmitted: goodbyeSubmittedByMe,
       );
     } catch (e) {
       // ignore: avoid_print
@@ -175,6 +183,7 @@ class Chat extends _$Chat {
       }
 
       final isClosing = sessionStatus == SessionStatus.closing;
+      final goodbyeSubmittedByMe = sessionData?['goodbye_submitted_by_me'] as bool? ?? false;
 
       final response = await _apiClient.get('/api/shared/chat/$sessionId/messages');
       final messagesData = response['data'] as List<dynamic>;
@@ -215,6 +224,7 @@ class Chat extends _$Chat {
       state = ChatConnectedData(
         messages: messages,
         sessionClosing: isClosing,
+        goodbyeSubmitted: goodbyeSubmittedByMe,
       );
     } catch (e) {
       state = const ChatErrorData('Gagal terhubung ke chat.');