Phase 4 checkpoint: chat-screen perf refactor + retryable blast-failure + repo-wide dispose-ref guardrail

Chat-screen performance (customer + mitra):
- Parent screens have zero `ref.watch` — only `ref.listen` for side effects
- Body extracted into its own `ConsumerStatefulWidget`; AppBar parts split
  into narrow `.select` consumers (mode, sensitivity, timer)
- Per-second timer ticks routed to dedicated providers
  (`chatRemainingSecondsProvider` + new `mitraChatRemainingSecondsProvider`)
  so WS `session_tick` frames don't invalidate the rest of the chat state

Dispose-in-ref bug fix:
- `home_screen.dart`, `payment_screen.dart`, `mitra_chat_screen.dart` —
  ref-using cleanup moved from `dispose()` to `deactivate()`. Modern
  Riverpod invalidates `ref` the moment `dispose()` runs; the resulting
  silent error corrupts the widget-tree finalize and the next screen
  appears frozen
- `halo_lints` package added at repo root with `no_ref_in_dispose` rule
  to catch this pattern in CI / IDE analysis
- `custom_lint` activated in both apps' `analysis_options.yaml`
  (was installed but never wired in — also brings `riverpod_lint`'s
  `avoid_ref_inside_state_dispose` online)
- CLAUDE.md Pitfalls section added to client_app + mitra_app

Phase 4 §3 retryable blast-failure (Option A):
- Backend `expirePairingRequest` + all-rejected use
  `recordIntermediateFailure` instead of `failPaymentSession` so the
  payment session stays `confirmed` for re-blast
- WS `pairing_failed` payload carries `is_terminal: false` on the
  retryable paths; client parses the flag and exposes `retryBlast()`
- "Coba cari lagi" CTA on S7 Timeout now re-blasts on the same payment
- Pairing service test updated to reflect the new semantics

Customer waiting-payment screen navigation patch:
- `_navigateTerminal` uses `Future.microtask` + `addPostFrameCallback`
  redundancy after a release-mode bug where polling stopped but
  `context.go` never fired, leaving the screen visually stuck on
  "menunggu pembayaran"

See requirement/resume-2026-05-15.md for next-day pickup checklist
(mitra release rebuild + S21 Ultra install + retest is the gating item).

Bundles unrelated in-flight Phase 4 §2.x work that was already on disk
(ESP screen removal, USP one-time gate scaffolding, bestie-availability
public route, OTP service edits, Maestro flow tweaks) — kept together
to avoid a partial-rebase mess.

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

client_app/lib/features/payment/screens/payment_screen.dart

@@ -60,13 +60,16 @@ class _PaymentScreenState extends ConsumerState<PaymentScreen> {
   }
 
   @override
-  void dispose() {
-    // Best-effort cancel on back/dispose if we still have a `pending` row.
+  void deactivate() {
+    // Best-effort cancel on back/leave if we still have a `pending` row.
     // The notifier checks state before calling the API, so this is safe to
-    // call unconditionally.
+    // call unconditionally. Lives in deactivate(), not dispose(), because
+    // modern Riverpod invalidates `ref` once dispose() starts — the resulting
+    // `Bad state: Cannot use "ref" after the widget was disposed.` corrupts
+    // the widget-tree finalize and leaves the next screen frozen.
     // ignore: discarded_futures
     ref.read(paymentProvider.notifier).cancelIfPending();
-    super.dispose();
+    super.deactivate();
   }
 
 

client_app/lib/features/payment/screens/waiting_payment_screen.dart

@@ -125,20 +125,35 @@ class _WaitingPaymentScreenState extends ConsumerState<WaitingPaymentScreen>
     if (status == PaymentSessionStatus.confirmed ||
         status == PaymentSessionStatus.consumed) {
       _markTerminal();
-      WidgetsBinding.instance.addPostFrameCallback((_) {
-        if (!mounted) return;
-        context.go('/onboarding/notif-gate');
-      });
+      _navigateTerminal('/onboarding/notif-gate');
     } else if (status == PaymentSessionStatus.expired ||
         status == PaymentSessionStatus.abandoned) {
       _markTerminal();
-      WidgetsBinding.instance.addPostFrameCallback((_) {
-        if (!mounted) return;
-        context.go('/payment/expired/${widget.paymentId}');
-      });
+      _navigateTerminal('/payment/expired/${widget.paymentId}');
     }
   }
 
+  /// Routes off the waiting screen once the payment session reached a
+  /// terminal status. Belt-and-braces:
+  ///   - `Future.microtask` runs after the current event loop turn (after any
+  ///     pending setState), so we don't fight an in-flight build.
+  ///   - `addPostFrameCallback` is a fallback in case the microtask is
+  ///     pre-empted (observed once on release builds where the screen stayed
+  ///     visually stuck on "menunggu pembayaran" despite polling having
+  ///     stopped — see 2026-05-14 thread).
+  void _navigateTerminal(String route) {
+    Future.microtask(() {
+      if (!mounted) return;
+      context.go(route);
+    });
+    WidgetsBinding.instance.addPostFrameCallback((_) {
+      if (!mounted) return;
+      // No-op if the microtask already navigated — `go` to the same location
+      // is idempotent in GoRouter.
+      context.go(route);
+    });
+  }
+
   void _markTerminal() {
     _terminal = true;
     _ticker?.cancel();