Mitra: regression coverage for back-press-during-session-ended

Verified the 2026-05-15 disconnect() fix end-to-end on emulator-5556:
mitra logs in → online → accepts blast → backend force-expires →
goodbye composer renders → back-press → lands on Bestie Home with
online status preserved, zero flutter:E in logcat.

- ts-mitra-3-08-back_press_after_session_expired_no_red_screen.yaml
  codifies the repro for Maestro. Extends ts-mitra-3-04 with the
  back-tap + home-assertion + red-screen guard.
- mitra_app/CLAUDE.md adds a Pitfall section beneath the existing
  "no ref in dispose" rule: never mutate notifier state synchronously
  from deactivate() cleanup — wrap in
  SchedulerBinding.addPostFrameCallback or Riverpod throws "Tried to
  modify a provider while the widget tree was building" during the
  back-nav teardown.

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

mitra_app/.maestro/flows/ts-mitra-3-08-back_press_after_session_expired_no_red_screen.yaml

@@ -0,0 +1,131 @@
+# ts-mitra-3-08 — §3 Back-press after session expires returns to Home (regression)
+# Spec ref: requirement/flow_mitra.mermaid.md §3 + project-pending-mitra-chat-disconnect-fix
+#
+# Regression test for the 2026-05-15 fix in
+# mitra_app/lib/core/chat/mitra_chat_notifier.dart::disconnect() — the
+# synchronous `state = MitraChatInitialData()` used to fire from
+# mitra_chat_screen.dart::deactivate() during back-nav, notifying Riverpod
+# watchers while the widget tree was mid-teardown → red error screen.
+#
+# Fix: state reset is now deferred to a post-frame callback via
+# SchedulerBinding.addPostFrameCallback(...). If that fix regresses, this
+# flow will fail at the "back chevron" step — the chat screen either stays
+# put (no nav because the engine restarted) or the Home tab assertions miss
+# because Flutter is showing its red error screen.
+#
+# Walks (extends ts-mitra-3-04):
+#   1. Seed + sign in + online + accept blast → /chat/session/:id
+#   2. force-session-expires-at (-1s) → backend fires session_expired WS
+#   3. Wait for ended-state chrome (proves WS frame landed)
+#   4. Tap back chevron on the chat AppBar
+#   5. Assert mitra is back on Home (Bestie greeting + tile grid visible)
+#   6. Assert no Flutter red-screen text leaked through
+appId: com.mybestie.mitra
+env:
+  TEST_PHONE: "+628200000908"
+  MITRA_DISPLAY_NAME: "Maestro BackNav"
+  BACKEND_INTERNAL_URL: http://localhost:3001
+---
+- runScript:
+    file: ../scripts/seed_mitra.js
+    env:
+      TEST_PHONE: ${TEST_PHONE}
+      MITRA_DISPLAY_NAME: ${MITRA_DISPLAY_NAME}
+      IS_ACTIVE: "true"
+      BACKEND_INTERNAL_URL: ${BACKEND_INTERNAL_URL}
+- runScript:
+    file: ../scripts/reset_phone.js
+    env:
+      TEST_PHONE: ${TEST_PHONE}
+      BACKEND_INTERNAL_URL: ${BACKEND_INTERNAL_URL}
+
+- launchApp:
+    clearState: true
+- extendedWaitUntil:
+    visible:
+      text: "(?s).*Halo Mitra Bestie.*"
+    timeout: 10000
+
+- tapOn:
+    point: "50%, 53%"
+- inputText: "8200000908"
+- tapOn: "(?s).*kirim kode.*"
+- extendedWaitUntil:
+    visible:
+      text: "(?s).*masukin 6 digit kode.*"
+    timeout: 10000
+- runScript:
+    file: ../scripts/peek_otp.js
+    env:
+      TEST_PHONE: ${TEST_PHONE}
+      BACKEND_INTERNAL_URL: ${BACKEND_INTERNAL_URL}
+- inputText: ${output.OTP}
+
+- extendedWaitUntil:
+    visible:
+      text: "(?s).*Kamu lagi (ONLINE|OFFLINE).*"
+    timeout: 15000
+
+- runFlow:
+    when:
+      visible:
+        text: "(?s).*Kamu lagi OFFLINE.*"
+    commands:
+      - tapOn: "(?s).*Nyalain Status.*"
+      - extendedWaitUntil:
+          visible:
+            text: "(?s).*Kamu lagi ONLINE.*"
+          timeout: 10000
+
+- waitForAnimationToEnd:
+    timeout: 3000
+
+- runScript: ../scripts/customer_blast_now.js
+- extendedWaitUntil:
+    visible:
+      text: "(?s).*Curhat Baru!.*"
+    timeout: 10000
+
+- tapOn: "(?s).*Terima.*"
+
+- extendedWaitUntil:
+    visible:
+      text: "(?s).*sesi aktif · Chat.*"
+    timeout: 15000
+
+# Force-expire the active session → ended chrome renders.
+- runScript:
+    file: ../scripts/force_session_expires_at.js
+    env:
+      BACKEND_INTERNAL_URL: ${BACKEND_INTERNAL_URL}
+
+- extendedWaitUntil:
+    visible:
+      text: "(?s).*Durasi sesi habis.*"
+    timeout: 15000
+
+# The regression-trigger moment: tap back while the chat screen is in
+# expired state. Pre-fix this raised the Flutter red-screen and the
+# engine restarted; the user landed back on /login. Post-fix the back
+# chevron pops to Home cleanly.
+#
+# The chevron is `IconButton(Icons.chevron_left)` with no semantics label,
+# so we tap by AppBar leading position. 8% from each edge hits the icon
+# center reliably on the standard mitra emulator (5556 → Pixel 6 / 1080w).
+- tapOn:
+    point: "8%, 8%"
+
+# Post-back assertions: we're on Home (Bestie shell).
+- extendedWaitUntil:
+    visible:
+      text: "(?s).*Kamu lagi (ONLINE|OFFLINE).*"
+    timeout: 8000
+- assertVisible: "(?s).*Halo, ${MITRA_DISPLAY_NAME}.*"
+
+# Sanity: Flutter red-screen text never leaked through. Flutter's default
+# debug error widget renders "EXCEPTION CAUGHT BY" and a stack trace; if
+# either is visible the disconnect fix has regressed.
+- assertNotVisible: "(?s).*EXCEPTION CAUGHT BY.*"
+- assertNotVisible: "(?s).*Tried to modify a provider.*"
+
+- takeScreenshot: ts-mitra-3-08-back-press-no-red-screen