Mitra chat: real customer name + ticking timer + goodbye pill

Four small fixes on the mitra chat screen, all surfacing through the
chat connected-state.

1. AppBar customer name. The hardcoded "Customer" only ever came from
   the FCM-tap navigation fallback (notification_service:
   `extra: {'customerName': 'Customer'}`); the popup-overlay path passes
   the real name but FCM had no way to know it. /chat/:sessionId/info
   already returns `customer_display_name` — propagate it into
   MitraChatConnectedData and read in the AppBar via .select. Falls
   back to the route arg for the brief connecting window.

2. SISA WAKTU stuck at --:--. The pill watches a remaining-seconds
   provider that's only updated by backend WS frames. Backend only
   fires session_timer at 3-min + 1-min warnings + expiry, so the pill
   sat at --:-- for the first ~7 minutes of a 10-min chat. Added a
   local 1s ticker in the notifier that drives the provider against
   expires_at (also pulled from /info). WS warning frames still
   overwrite normally on top.

3. Pesan Penutup textbox. Replaced the rounded-rect OutlineInputBorder
   field with a fixed-height Container pill whose border matches the
   previous "shadow" tone (HaloTokens.border). Pill borderRadius is
   the full 100 (was 12).

4. Goodbye textbox text was top-aligned because maxLines: 3 +
   OutlineInputBorder left vertical alignment to InputDecoration's
   built-in padding. Switched to maxLines: 1 + textAlignVertical:
   center + isCollapsed: true inside the fixed-height container —
   text now sits on the vertical center.

Bonus: the goodbye subhead "Tuliskan pesan terakhirmu untuk Customer"
also picked up the real name ("…untuk Andi Pratama").

Verified end-to-end on emulator-5556 (TestMitra-1501 + customer
"Andi Pratama"): AppBar shows Andi Pratama, SISA WAKTU ticks (04:57 →
04:35 across screenshots), goodbye pill renders with centered hint.

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

mitra_app/lib/core/chat/mitra_chat_notifier.dart

@@ -61,6 +61,12 @@ class MitraChatConnectedData extends MitraChatData {
   final List<String> topics;
   // Phase 4 — voice-call mode badge in header. `chat` is the default (no pill).
   final SessionMode mode;
+  // Customer display name + session deadline pulled from /info on connect.
+  // AppBar reads displayName (falls back to route-arg "Customer" when null);
+  // the timer pill ticks down against expiresAt via a local 1s ticker so it
+  // doesn't sit at --:-- waiting for a server warning frame.
+  final String? customerDisplayName;
+  final DateTime? expiresAt;
 
   const MitraChatConnectedData({
     required this.messages,
@@ -73,6 +79,8 @@ class MitraChatConnectedData extends MitraChatData {
     this.topicSensitivity = TopicSensitivity.regular,
     this.topics = const [],
     this.mode = SessionMode.chat,
+    this.customerDisplayName,
+    this.expiresAt,
   });
 
   MitraChatConnectedData copyWith({
@@ -87,6 +95,8 @@ class MitraChatConnectedData extends MitraChatData {
     TopicSensitivity? topicSensitivity,
     List<String>? topics,
     SessionMode? mode,
+    String? customerDisplayName,
+    DateTime? expiresAt,
   }) {
     return MitraChatConnectedData(
       messages: messages ?? this.messages,
@@ -99,6 +109,8 @@ class MitraChatConnectedData extends MitraChatData {
       topicSensitivity: topicSensitivity ?? this.topicSensitivity,
       topics: topics ?? this.topics,
       mode: mode ?? this.mode,
+      customerDisplayName: customerDisplayName ?? this.customerDisplayName,
+      expiresAt: expiresAt ?? this.expiresAt,
     );
   }
 }
@@ -143,6 +155,11 @@ class MitraChat extends _$MitraChat {
   WebSocketChannel? _channel;
   StreamSubscription? _wsSubscription;
   Timer? _typingTimer;
+  // Local 1s ticker that updates mitraChatRemainingSecondsProvider against
+  // the session's expires_at. Backend's session_timer WS frames only fire
+  // at 3min + 1min warnings + expiry — without this ticker the pill stays
+  // at --:-- for most of the session.
+  Timer? _countdownTimer;
   // Survives `disconnect()` so a later `didChangeAppLifecycleState(resumed)`
   // can re-issue `connect(sessionId)` with the right session — disconnect()
   // resets `state` to MitraChatInitialData, which is otherwise the only
@@ -178,6 +195,9 @@ class MitraChat extends _$MitraChat {
       final espTopics = rawTopics is List
           ? rawTopics.whereType<String>().toList(growable: false)
           : const <String>[];
+      final customerDisplayName = sessionData?['customer_display_name'] as String?;
+      final expiresAtRaw = sessionData?['expires_at'] as String?;
+      final expiresAt = expiresAtRaw == null ? null : DateTime.tryParse(expiresAtRaw);
 
       // If the customer requested an extension while we were off-WS (e.g.
       // mitra on Home, app backgrounded, FCM tap cold-started us here),
@@ -230,7 +250,13 @@ class MitraChat extends _$MitraChat {
         topics: espTopics,
         mode: sessionMode,
         extensionRequest: pendingExt,
+        customerDisplayName: customerDisplayName,
+        expiresAt: expiresAt,
       );
+
+      // Kick off the 1s ticker if we have a deadline. Updates the auto-dispose
+      // remaining-seconds provider used by the timer pill.
+      if (expiresAt != null) _startCountdownTicker(expiresAt);
     } catch (e) {
       state = const MitraChatErrorData('Gagal terhubung ke chat.');
     }
@@ -413,5 +439,23 @@ class MitraChat extends _$MitraChat {
     _channel = null;
     _typingTimer?.cancel();
     _typingTimer = null;
+    _countdownTimer?.cancel();
+    _countdownTimer = null;
+  }
+
+  /// Drives the remaining-seconds provider every second against [deadline].
+  /// Backend session_timer WS frames still arrive (3min/1min warnings,
+  /// expiry) — they overwrite via the existing _onMessageReceived handler.
+  /// On extension accept the connect() flow re-runs (sessionData refreshes)
+  /// and the new deadline restarts the ticker.
+  void _startCountdownTicker(DateTime deadline) {
+    _countdownTimer?.cancel();
+    void tick() {
+      final remaining = deadline.difference(DateTime.now()).inSeconds;
+      final clamped = remaining < 0 ? 0 : remaining;
+      ref.read(mitraChatRemainingSecondsProvider.notifier).update(clamped);
+    }
+    tick(); // initial paint — don't wait a second for the first value
+    _countdownTimer = Timer.periodic(const Duration(seconds: 1), (_) => tick());
   }
 }