feat(android): Phase 11 Commit B — ServerUrl entry + auth-gated startDestination

Cold launch now lands on the right screen based on persisted auth
state instead of always starting at Home.

New:
  - auth/ui/AuthGateViewModel.kt — one-shot StateFlow that resolves
    the initial NavHost destination from AuthSessionDao directly
    (not AuthStore.sessionCookie, which is null until Room's first
    async emission). Three outcomes:
      no row at all                                → ServerUrl
      row with default URL and no cookie           → ServerUrl
      row with cookie absent / empty               → Login
      row with cookie present                      → Home
  - auth/ui/ServerUrlScreen.kt — VM + Screen in one file (still under
    the function-count cap). Validates `http(s)://` prefix +
    non-empty, trims trailing slash before persisting. On success
    navigates to Login and pops ServerUrl off the back stack.

Modified:
  - MainActivity.kt — wraps the NavGraph in an App() composable that
    reads the AuthGateViewModel. Renders a centered spinner
    (BootSplash) while the gate resolves; once resolved, hands the
    decision to MinstrelNavGraph as `startDestination`.
  - nav/MinstrelNavGraph.kt — startDestination is now a parameter
    (was hardcoded to Home). ServerUrl route renders the real screen
    instead of ComingSoon.

Settings (with sign-out) is Commit C; cross-restart user identity
persistence + auth-error 401 redirect handling are later refinements.

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

android/app/src/main/java/com/fabledsword/minstrel/MainActivity.kt

@@ -4,10 +4,18 @@ import android.os.Bundle
 import androidx.activity.ComponentActivity
 import androidx.activity.compose.setContent
 import androidx.activity.enableEdgeToEdge
+import androidx.compose.foundation.layout.Box
 import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.material3.CircularProgressIndicator
+import androidx.compose.material3.MaterialTheme
 import androidx.compose.runtime.Composable
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Alignment
 import androidx.compose.ui.Modifier
+import androidx.hilt.navigation.compose.hiltViewModel
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
 import androidx.navigation.compose.rememberNavController
+import com.fabledsword.minstrel.auth.ui.AuthGateViewModel
 import com.fabledsword.minstrel.nav.MinstrelNavGraph
 import com.fabledsword.minstrel.theme.MinstrelTheme
 import dagger.hilt.android.AndroidEntryPoint
@@ -24,12 +32,29 @@ class MainActivity : ComponentActivity() {
 }
 
 @Composable
-private fun App() {
-    // No bottom nav, no drawer — navigation is per-screen via the
-    // AppBar actions row + kebab (`MainAppBarActions`). The MiniPlayer
-    // is included by each in-shell route's `ShellScaffold` wrap;
-    // full-screen routes (NowPlaying / Queue / unauthenticated) bypass
-    // the shell entirely.
-    val navController = rememberNavController()
-    MinstrelNavGraph(navController = navController, modifier = Modifier.fillMaxSize())
+private fun App(gate: AuthGateViewModel = hiltViewModel()) {
+    val startDestination by gate.startDestination.collectAsStateWithLifecycle()
+    val resolved = startDestination
+    if (resolved == null) {
+        BootSplash()
+    } else {
+        // No bottom nav, no drawer — navigation is per-screen via the
+        // AppBar actions row + kebab (`MainAppBarActions`). The MiniPlayer
+        // is included by each in-shell route's `ShellScaffold` wrap;
+        // full-screen routes (NowPlaying / Queue / unauthenticated)
+        // bypass the shell entirely.
+        val navController = rememberNavController()
+        MinstrelNavGraph(
+            navController = navController,
+            startDestination = resolved,
+            modifier = Modifier.fillMaxSize(),
+        )
+    }
+}
+
+@Composable
+private fun BootSplash() {
+    Box(modifier = Modifier.fillMaxSize(), contentAlignment = Alignment.Center) {
+        CircularProgressIndicator(color = MaterialTheme.colorScheme.primary)
+    }
 }

android/app/src/main/java/com/fabledsword/minstrel/auth/ui/AuthGateViewModel.kt

@@ -0,0 +1,51 @@
+package com.fabledsword.minstrel.auth.ui
+
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.viewModelScope
+import com.fabledsword.minstrel.auth.AuthStore
+import com.fabledsword.minstrel.cache.db.dao.AuthSessionDao
+import com.fabledsword.minstrel.nav.Home
+import com.fabledsword.minstrel.nav.Login
+import com.fabledsword.minstrel.nav.ServerUrl
+import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.launch
+import javax.inject.Inject
+
+/**
+ * Computes the initial startDestination for the root NavHost based on
+ * persisted auth state. Sits on top of AuthSessionDao directly rather
+ * than AuthStore's StateFlow because the StateFlow defaults to null
+ * until Room's first async emission — we need a definitive answer
+ * before drawing any nav graph.
+ *
+ *   - no row at all          → ServerUrl   (first launch)
+ *   - row with baseUrl, no cookie → Login   (URL configured, not yet signed in)
+ *   - row with cookie        → Home        (signed in)
+ *
+ * `startDestination` emits null while resolving (UI shows a spinner)
+ * and then exactly one resolved value.
+ */
+@HiltViewModel
+class AuthGateViewModel @Inject constructor(
+    private val dao: AuthSessionDao,
+) : ViewModel() {
+
+    private val internal = MutableStateFlow<Any?>(null)
+    val startDestination: StateFlow<Any?> = internal.asStateFlow()
+
+    init {
+        viewModelScope.launch {
+            val row = dao.get()
+            internal.value = when {
+                row == null -> ServerUrl
+                row.baseUrl == AuthStore.DEFAULT_BASE_URL && row.sessionCookie.isNullOrEmpty() ->
+                    ServerUrl
+                row.sessionCookie.isNullOrEmpty() -> Login
+                else -> Home
+            }
+        }
+    }
+}

android/app/src/main/java/com/fabledsword/minstrel/auth/ui/ServerUrlScreen.kt

@@ -0,0 +1,163 @@
+package com.fabledsword.minstrel.auth.ui
+
+import androidx.compose.foundation.layout.Arrangement
+import androidx.compose.foundation.layout.Box
+import androidx.compose.foundation.layout.Column
+import androidx.compose.foundation.layout.fillMaxSize
+import androidx.compose.foundation.layout.fillMaxWidth
+import androidx.compose.foundation.layout.padding
+import androidx.compose.foundation.text.KeyboardActions
+import androidx.compose.foundation.text.KeyboardOptions
+import androidx.compose.material3.Button
+import androidx.compose.material3.MaterialTheme
+import androidx.compose.material3.OutlinedTextField
+import androidx.compose.material3.Text
+import androidx.compose.runtime.Composable
+import androidx.compose.runtime.LaunchedEffect
+import androidx.compose.runtime.getValue
+import androidx.compose.ui.Alignment
+import androidx.compose.ui.Modifier
+import androidx.compose.ui.text.input.ImeAction
+import androidx.compose.ui.text.input.KeyboardType
+import androidx.compose.ui.unit.dp
+import androidx.hilt.navigation.compose.hiltViewModel
+import androidx.lifecycle.ViewModel
+import androidx.lifecycle.compose.collectAsStateWithLifecycle
+import androidx.lifecycle.viewModelScope
+import androidx.navigation.NavHostController
+import com.fabledsword.minstrel.auth.AuthStore
+import com.fabledsword.minstrel.nav.Login
+import com.fabledsword.minstrel.nav.ServerUrl
+import dagger.hilt.android.lifecycle.HiltViewModel
+import kotlinx.coroutines.flow.MutableStateFlow
+import kotlinx.coroutines.flow.StateFlow
+import kotlinx.coroutines.flow.asStateFlow
+import kotlinx.coroutines.flow.update
+import kotlinx.coroutines.launch
+import javax.inject.Inject
+
+// ─── State + VM ───────────────────────────────────────────────────────
+
+data class ServerUrlFormState(
+    val url: String = "",
+    val saving: Boolean = false,
+    val saved: Boolean = false,
+    val errorMessage: String? = null,
+)
+
+@HiltViewModel
+class ServerUrlViewModel @Inject constructor(
+    private val authStore: AuthStore,
+) : ViewModel() {
+
+    private val internal = MutableStateFlow(
+        ServerUrlFormState(url = authStore.baseUrl.value),
+    )
+    val state: StateFlow<ServerUrlFormState> = internal.asStateFlow()
+
+    fun setUrl(value: String) {
+        internal.update { it.copy(url = value, errorMessage = null) }
+    }
+
+    fun submit() {
+        val raw = internal.value.url.trim().trimEnd('/')
+        if (raw.isEmpty()) {
+            internal.update { it.copy(errorMessage = "Enter a server URL.") }
+            return
+        }
+        if (!raw.startsWith("http://") && !raw.startsWith("https://")) {
+            internal.update {
+                it.copy(errorMessage = "URL must start with http:// or https://")
+            }
+            return
+        }
+        viewModelScope.launch {
+            internal.update { it.copy(saving = true, errorMessage = null) }
+            authStore.setBaseUrl(raw)
+            internal.update { it.copy(saving = false, saved = true) }
+        }
+    }
+
+    fun consumeSaved() {
+        internal.update { it.copy(saved = false) }
+    }
+}
+
+// ─── Screen ───────────────────────────────────────────────────────────
+
+@Composable
+fun ServerUrlScreen(
+    navController: NavHostController,
+    viewModel: ServerUrlViewModel = hiltViewModel(),
+) {
+    val state by viewModel.state.collectAsStateWithLifecycle()
+
+    LaunchedEffect(state.saved) {
+        if (state.saved) {
+            navController.navigate(Login) {
+                popUpTo(ServerUrl) { inclusive = true }
+            }
+            viewModel.consumeSaved()
+        }
+    }
+
+    Box(modifier = Modifier.fillMaxSize()) {
+        ServerUrlForm(
+            state = state,
+            onUrlChange = viewModel::setUrl,
+            onSubmit = viewModel::submit,
+        )
+    }
+}
+
+@Composable
+private fun ServerUrlForm(
+    state: ServerUrlFormState,
+    onUrlChange: (String) -> Unit,
+    onSubmit: () -> Unit,
+) {
+    Column(
+        modifier = Modifier
+            .fillMaxSize()
+            .padding(24.dp),
+        verticalArrangement = Arrangement.spacedBy(16.dp, Alignment.CenterVertically),
+        horizontalAlignment = Alignment.CenterHorizontally,
+    ) {
+        Text(
+            text = "Connect to your Minstrel",
+            style = MaterialTheme.typography.headlineMedium,
+            color = MaterialTheme.colorScheme.onBackground,
+        )
+        Text(
+            text = "Enter the URL of your Minstrel server.",
+            style = MaterialTheme.typography.bodyMedium,
+            color = MaterialTheme.colorScheme.onSurfaceVariant,
+        )
+        OutlinedTextField(
+            value = state.url,
+            onValueChange = onUrlChange,
+            modifier = Modifier.fillMaxWidth(),
+            label = { Text("Server URL") },
+            placeholder = { Text("https://minstrel.example.com") },
+            singleLine = true,
+            enabled = !state.saving,
+            keyboardOptions = KeyboardOptions(
+                keyboardType = KeyboardType.Uri,
+                imeAction = ImeAction.Done,
+            ),
+            keyboardActions = KeyboardActions(onDone = { onSubmit() }),
+        )
+        if (state.errorMessage != null) {
+            Text(
+                text = state.errorMessage,
+                color = MaterialTheme.colorScheme.error,
+                style = MaterialTheme.typography.bodySmall,
+            )
+        }
+        Button(
+            onClick = onSubmit,
+            enabled = !state.saving && state.url.isNotBlank(),
+            modifier = Modifier.fillMaxWidth(),
+        ) { Text("Continue") }
+    }
+}

android/app/src/main/java/com/fabledsword/minstrel/nav/MinstrelNavGraph.kt

@@ -15,6 +15,7 @@ import com.fabledsword.minstrel.admin.ui.AdminQuarantineScreen
 import com.fabledsword.minstrel.admin.ui.AdminRequestsScreen
 import com.fabledsword.minstrel.admin.ui.AdminUsersScreen
 import com.fabledsword.minstrel.auth.ui.LoginScreen
+import com.fabledsword.minstrel.auth.ui.ServerUrlScreen
 import com.fabledsword.minstrel.discover.ui.DiscoverScreen
 import com.fabledsword.minstrel.home.ui.HomeScreen
 import com.fabledsword.minstrel.library.ui.LibraryScreen
@@ -36,12 +37,13 @@ import com.fabledsword.minstrel.shared.widgets.ShellScaffold
 @Composable
 fun MinstrelNavGraph(
     navController: NavHostController,
+    startDestination: Any,
     modifier: Modifier = Modifier,
 ) {
     val expandPlayer = { navController.navigate(NowPlaying) }
     NavHost(
         navController = navController,
-        startDestination = Home,
+        startDestination = startDestination,
         modifier = modifier.fillMaxSize(),
     ) {
         inShellTopLevel(navController, expandPlayer)
@@ -146,9 +148,7 @@ private fun NavGraphBuilder.outsideShell(navController: NavHostController) {
         NowPlayingScreen()
     }
     composable<Queue> { ComingSoon("Queue", "Lands in a later 6.x slice.") }
-    composable<ServerUrl> {
-        ComingSoon("Connect to your Minstrel", "Server-URL entry — Phase 11.")
-    }
+    composable<ServerUrl> { ServerUrlScreen(navController = navController) }
     composable<Login> { LoginScreen(navController = navController) }
 }