test(settings): cancel viewModelScope before db.close in SignaturesScreenTest to fix a Room teardown race (flaky on API-37 CI)

SignaturesScreenTest built a real SignaturesViewModel by hand but tore down
with a bare `db.close()` that never cancelled viewModelScope. The ViewModel's
`signatures` StateFlow is a Room InvalidationTracker Flow kept alive by
stateIn(WhileSubscribed(5_000)), so the collector could stay live up to 5s
after the UI detached — a re-query then landed on the just-closed in-memory DB
and threw SQLITE_MISUSE ("connection is closed"). Timing-dependent, hence the
intermittent API-37 CI failure in tappingRadioOnNonDefault_makesItTheDefault.

Fix: hold the ViewModel in an androidx.lifecycle.ViewModelStore and, in @After,
call store.clear() (→ ViewModel.onCleared() → cancels viewModelScope) BEFORE
db.close(), so the collector is gone before the DB closes. Behaviour and
assertions are unchanged; the fix removes the race by construction.

Audited the androidTest tree for the same hazard and fixed two siblings the
same way:
- AccountSettingsScreenTest: had the same live-Room-Flow-vs-close race,
  previously worked around by never closing the in-memory DB at all; now
  clears the ViewModel then closes the DB.
- ComposeScreenTest: ComposeViewModel's init launches a viewModelScope
  coroutine that reads the real accountSettings/signature Room repos; clear
  the store before db.close() to avoid the same in-flight-read-vs-close race.

Verified locally: connectedDebugAndroidTest green for all three classes
(12/12) on a cold-booted emulator, plus the JVM fast gate (assembleDebug,
testDebugUnitTest, jacocoTestCoverageVerification, compileDebugAndroidTestKotlin,
lintDebug, ktlintCheck, detekt).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

app/src/androidTest/kotlin/org/libremail/ui/compose/ComposeScreenTest.kt

@@ -15,6 +15,7 @@ import androidx.compose.ui.test.onNodeWithText
 import androidx.compose.ui.test.performClick
 import androidx.compose.ui.test.performTextInput
 import androidx.lifecycle.SavedStateHandle
+import androidx.lifecycle.ViewModelStore
 import androidx.room.Room
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import androidx.test.platform.app.InstrumentationRegistry
@@ -60,10 +61,20 @@ class ComposeScreenTest {
 
     private var db: AccountDatabase? = null
 
+    // Holds the real ComposeViewModel built by hand in setContent() below, so closeDb() can clear()
+    // it (triggering ViewModel.onCleared()) before closing the DB.
+    private val viewModelStore = ViewModelStore()
+
     private fun string(resId: Int) = composeTestRule.activity.getString(resId)
 
     @After
     fun closeDb() {
+        // Clear the store (→ ViewModel.onCleared() → cancels viewModelScope) BEFORE closing the DB.
+        // ComposeViewModel's init block launches a viewModelScope coroutine that reads the real
+        // accountSettings/signature Room repositories (applySignature()); without this, that read can
+        // still be in flight when the DB closes, racing a SQLITE_MISUSE ("connection is closed") —
+        // the same class of teardown race fixed in SignaturesScreenTest/AccountSettingsScreenTest.
+        viewModelStore.clear()
         db?.close()
     }
 
@@ -92,6 +103,7 @@ class ComposeScreenTest {
             signatureRepository = SignatureRepository(database.signatureDao()),
             settingsRepository = SettingsRepository(context),
         )
+        viewModelStore.put("compose", viewModel)
         composeTestRule.setContent {
             LibreMailTheme(darkTheme = false, dynamicColor = false) {
                 ComposeScreen(onBack = onBack, viewModel = viewModel)

app/src/androidTest/kotlin/org/libremail/ui/settings/AccountSettingsScreenTest.kt

@@ -7,11 +7,13 @@ import androidx.compose.ui.test.junit4.createAndroidComposeRule
 import androidx.compose.ui.test.onNodeWithText
 import androidx.compose.ui.test.performClick
 import androidx.lifecycle.SavedStateHandle
+import androidx.lifecycle.ViewModelStore
 import androidx.room.Room
 import androidx.test.core.app.ApplicationProvider
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import androidx.work.WorkManager
 import kotlinx.coroutines.runBlocking
+import org.junit.After
 import org.junit.Rule
 import org.junit.Test
 import org.junit.runner.RunWith
@@ -54,13 +56,27 @@ class AccountSettingsScreenTest {
 
     private var manageSignaturesClicked = false
 
+    private lateinit var db: AccountDatabase
+
+    // Holds the real AccountSettingsViewModel built by hand in setContent() below, so tearDown() can
+    // clear() it (triggering ViewModel.onCleared()) before closing the DB.
+    private val viewModelStore = ViewModelStore()
+
+    @After
+    fun tearDown() {
+        // Clear the store (→ ViewModel.onCleared() → cancels viewModelScope) BEFORE closing the DB.
+        // The ViewModel's `settings`/`signatureCount`/`defaultSignatureName`/`account` Room
+        // InvalidationTracker Flows are kept alive by stateIn(WhileSubscribed(5_000)): without this,
+        // a collector can still be live up to 5s after the UI detaches, so a re-query lands on the
+        // just-closed in-memory DB and throws SQLITE_MISUSE ("connection is closed") — an intermittent
+        // teardown race, not a real bug. (Previously worked around by never closing the DB at all.)
+        viewModelStore.clear()
+        db.close()
+    }
+
     private fun setContent(): AccountSettingsRepository {
         val context = ApplicationProvider.getApplicationContext<Context>()
-        // Intentionally not closed in an @After: the ViewModel's `settings` Room Flow (kept alive by
-        // stateIn/WhileSubscribed) keeps querying after the test body, so closing the in-memory DB out
-        // from under it races and crashes ("connection pool has been closed"). The DB is reclaimed with
-        // the test process.
-        val db = Room.inMemoryDatabaseBuilder(context, AccountDatabase::class.java).build()
+        db = Room.inMemoryDatabaseBuilder(context, AccountDatabase::class.java).build()
         val repository = AccountSettingsRepository(db.accountSettingsDao())
         runBlocking {
             db.accountDao().upsert(account.toEntity()) // FK parent for the account_settings row
@@ -74,6 +90,7 @@ class AccountSettingsScreenTest {
             syncScheduler = SyncScheduler(Provider { WorkManager.getInstance(context) }),
             settingsRepository = SettingsRepository(context),
         )
+        viewModelStore.put("account-settings", viewModel)
         composeTestRule.setContent {
             LibreMailTheme(darkTheme = false, dynamicColor = false) {
                 AccountSettingsScreen(

app/src/androidTest/kotlin/org/libremail/ui/settings/SignaturesScreenTest.kt

@@ -14,6 +14,7 @@ import androidx.compose.ui.test.onAllNodesWithText
 import androidx.compose.ui.test.onNodeWithText
 import androidx.compose.ui.test.performClick
 import androidx.lifecycle.SavedStateHandle
+import androidx.lifecycle.ViewModelStore
 import androidx.room.Room
 import androidx.test.ext.junit.runners.AndroidJUnit4
 import androidx.test.platform.app.InstrumentationRegistry
@@ -50,6 +51,10 @@ class SignaturesScreenTest {
     private lateinit var db: AccountDatabase
     private lateinit var repository: SignatureRepository
 
+    // Holds the real SignaturesViewModel built by hand in setContent() below, so tearDown() can
+    // clear() it (triggering ViewModel.onCleared()) before closing the DB.
+    private val viewModelStore = ViewModelStore()
+
     @Before
     fun setUp() {
         db = Room.inMemoryDatabaseBuilder(context, AccountDatabase::class.java).build()
@@ -70,7 +75,15 @@ class SignaturesScreenTest {
     }
 
     @After
-    fun tearDown() = db.close()
+    fun tearDown() {
+        // Clear the store (→ ViewModel.onCleared() → cancels viewModelScope) BEFORE closing the DB.
+        // SignaturesViewModel.signatures is a Room InvalidationTracker Flow kept alive by
+        // stateIn(WhileSubscribed(5_000)): without this, the collector can still be live up to 5s
+        // after the UI detaches, so a re-query lands on the just-closed in-memory DB and throws
+        // SQLITE_MISUSE ("connection is closed") — an intermittent teardown race, not a real bug.
+        viewModelStore.clear()
+        db.close()
+    }
 
     private fun string(resId: Int) = composeTestRule.activity.getString(resId)
 
@@ -81,6 +94,7 @@ class SignaturesScreenTest {
             SavedStateHandle(mapOf(Routes.SIGNATURES_ARG_ACCOUNT to accountId)),
             repository,
         )
+        viewModelStore.put("signatures", viewModel)
         composeTestRule.setContent {
             LibreMailTheme(darkTheme = false, dynamicColor = false) {
                 SignaturesScreen(onBack = {}, onEdit = {}, onAdd = {}, viewModel = viewModel)