Phase 4 Stage 6: chat-room countdown UX + voice-call mode pill

Customer chat screen:
- Voice-call header pill (mode == 'call' renders accent-colored pill;
  chat mode renders no pill).
- HaloSnackbar fires once per session at 180s remaining ('sisa 3 menit
  lagi ya 🤍'), driven by the backend session_warning WS event.
- Last-2-min danger styling: timer pill flips to HaloTokens.danger +
  bold JetBrainsMono when remaining <= 120s.
- Floating ChatExpiredBanner widget injected above the input bar when
  remaining hits 0 in closing-grace state. perpanjang -> existing
  pricing bottom sheet.
- pricing_bottom_sheet.dart rewritten to the 5-option layout with
  chat|call mode toggle (mirrors duration-pick from Stage 3).

Mitra chat screen: voice-call header pill only (no countdown UX per PRD).

Backend:
- session.service.js getSessionById JOINs payment_sessions so mode +
  expires_at ship in /api/shared/chat/:id/info.
- session-timer.service.js onThreeMinuteWarning now emits expires_at +
  remaining_seconds for client resync.
- Dev-only POST /internal/_test/force-session-expires-at clears the
  3-min flag, reschedules the timer, and broadcasts WS resync. Lets
  the Maestro flow drive 175s -> 90s -> 0s without waiting live.

New chatRemainingSeconds StreamProvider derived from expiresAt, fed by
session_warning / session_timer / session_expired resync messages
(plan referenced a secondsLeftProvider that didn't actually exist).

Maestro 06_chat_countdown.yaml + force_session_expires_at.js helper.

Out of scope: meet.google.com URL launching - url_launcher isn't a
client_app dependency and message bubbles render plain Text. Defer.

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

mitra_app/lib/core/chat/mitra_chat_notifier.dart

@@ -36,6 +36,8 @@ class MitraChatConnectedData extends MitraChatData {
   // info-only — does not affect matching, pricing, or routing. Sourced from
   // `chat_sessions.topics` via the session info payload.
   final List<String> topics;
+  // Phase 4 — voice-call mode badge in header. `chat` is the default (no pill).
+  final SessionMode mode;
 
   const MitraChatConnectedData({
     required this.messages,
@@ -47,6 +49,7 @@ class MitraChatConnectedData extends MitraChatData {
     this.extensionRequest,
     this.topicSensitivity = TopicSensitivity.regular,
     this.topics = const [],
+    this.mode = SessionMode.chat,
   });
 
   MitraChatConnectedData copyWith({
@@ -60,6 +63,7 @@ class MitraChatConnectedData extends MitraChatData {
     bool clearExtensionRequest = false,
     TopicSensitivity? topicSensitivity,
     List<String>? topics,
+    SessionMode? mode,
   }) {
     return MitraChatConnectedData(
       messages: messages ?? this.messages,
@@ -71,6 +75,7 @@ class MitraChatConnectedData extends MitraChatData {
       extensionRequest: clearExtensionRequest ? null : (extensionRequest ?? this.extensionRequest),
       topicSensitivity: topicSensitivity ?? this.topicSensitivity,
       topics: topics ?? this.topics,
+      mode: mode ?? this.mode,
     );
   }
 }
@@ -137,6 +142,7 @@ class MitraChat extends _$MitraChat {
       final isClosing = sessionStatus == SessionStatus.closing;
       final goodbyeSubmittedByMe = sessionData?['goodbye_submitted_by_me'] as bool? ?? false;
       final sessionTopic = TopicSensitivity.fromString(sessionData?['topic_sensitivity'] as String?);
+      final sessionMode = SessionMode.fromString(sessionData?['mode'] as String?);
       final rawTopics = sessionData?['topics'];
       final espTopics = rawTopics is List
           ? rawTopics.whereType<String>().toList(growable: false)
@@ -184,6 +190,7 @@ class MitraChat extends _$MitraChat {
         goodbyeSubmitted: goodbyeSubmittedByMe,
         topicSensitivity: sessionTopic,
         topics: espTopics,
+        mode: sessionMode,
       );
     } catch (e) {
       state = const MitraChatErrorData('Gagal terhubung ke chat.');

mitra_app/lib/core/constants.dart

@@ -62,6 +62,20 @@ enum RequestResponse {
   }
 }
 
+/// Session mode — chat or voice call. Mirrors backend `payment_sessions.mode`
+/// (added in Phase 4 stage 1). Mitra only reads this to render the header
+/// "Voice Call" pill — there is no functional difference from a regular chat.
+enum SessionMode {
+  chat('chat'),
+  call('call');
+
+  final String value;
+  const SessionMode(this.value);
+
+  static SessionMode fromString(String? v) =>
+      values.firstWhere((e) => e.value == v, orElse: () => SessionMode.chat);
+}
+
 /// Session topic sensitivity
 enum TopicSensitivity {
   regular('regular'),
@@ -112,6 +126,8 @@ class WsMessage {
   static const sessionCompleted = 'session_completed';
   static const sessionPaused = 'session_paused';
   static const sessionResumed = 'session_resumed';
+  // Phase 4 — `session_warning` is customer-only; the mitra never receives it.
+  // Kept here for symmetry with backend constants only.
 
   // Extension
   static const extensionRequest = 'extension_request';