fix(session): clamp the countdown to wall clock, correct two doc claims

Second review pass (Fable) cleared all six fixes; these are its leftovers.

- _reconcileElapsedTime() runs off the same suspend-blind Stopwatch, so after
  a long device sleep the countdown over-reports - and with the API
  unreachable nothing corrects it, which is precisely the state the app now
  stays in instead of disconnecting. It now takes the lesser of the Stopwatch
  value and the wall-clock deadline; the minimum, so a clock set backwards
  cannot extend a session.
- CHANGELOG claimed the alert covers "the tunnel reporting an error". It
  cannot: AppConfigs.V2RAY_STATES has no error state and the plugin's
  stateName when() ends in else -> "DISCONNECTED", so VpnStatus.error is
  unreachable from the status stream on Android.
- AGENTS.md file map still listed a setSessionExpiry bridge in
  power_settings.dart; no such symbol exists.

Co-Authored-By: Claude Opus 5 <[email protected]>

lib/logic/session_timer.dart

@@ -426,6 +426,20 @@ class SessionTimer extends ChangeNotifier with WidgetsBindingObserver {
     final elapsed = clock.elapsed.inSeconds;
     _remainingSeconds =
         (_remainingAtLastSync - elapsed).clamp(0, 1 << 31).toInt();
+
+    // The Stopwatch is CLOCK_MONOTONIC and stops while the device is
+    // suspended, so after a long sleep it over-reports - and with the server
+    // unreachable no sync arrives to correct it, which is exactly the state
+    // the app now stays in rather than disconnecting. Take whichever is
+    // smaller, never the wall clock alone: a clock set backwards must not be
+    // able to extend a session.
+    final deadline = _deadlineAt;
+    if (deadline != null) {
+      final byWallClock = deadline.difference(DateTime.now()).inSeconds;
+      if (byWallClock < _remainingSeconds) {
+        _remainingSeconds = byWallClock.clamp(0, 1 << 31).toInt();
+      }
+    }
   }
 
   @override