channels: load at launch, keep the opened channel selected (#32, #34)

Assembling the channel rows is slow, so it now starts when the app launches
instead of when the view is first opened; opening the view usually finds the
rows already there, and a second pass is skipped while one is in flight or the
data is still fresh (#32).

Coming back from a channel page re-selects the channel that was opened, scrolling
its row back to it, instead of snapping to the first one (#34).

Also drops the custom focusRestorer fallback added for #29: handing back a
requester whose card had scrolled out of composition crashed the app with
"FocusRequester is not initialized" when focus re-entered a scrolled row (hit on
the Channels screen). The plain restorer keeps the #29 behaviour without it.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

app/src/main/java/net/jeena/jtubetv/ui/screens/ChannelsScreen.kt

@@ -127,11 +127,17 @@ class ChannelsViewModel(private val store: TokenStore) : ViewModel() {
     // its shimmer placeholder rows until the (fast-path, few-request) load lands,
     // instead of painting a stale snapshot that reshuffled as stats streamed in.
 
+    /** Guards against a second pass while the first is still running (issue #32:
+     *  the load now starts at app launch, so opening the view can overlap it). */
+    private var inFlight = false
+
     fun load(force: Boolean = false) {
         // Re-entry (destination switch away + back) inside the freshness window:
         // repaint the in-memory rows and skip the network (issue #13) — rows are
         // never torn down on re-entry; an account switch builds a new ViewModel.
+        if (inFlight) return
         if (!force && userRows.isNotEmpty() && fresh()) return
+        inFlight = true
         loading = true
         error = null
         viewModelScope.launch {
@@ -160,6 +166,7 @@ class ChannelsViewModel(private val store: TokenStore) : ViewModel() {
                 error = e.message ?: "Could not load channels"
             } finally {
                 loading = false
+                inFlight = false
             }
         }
     }
@@ -310,6 +317,8 @@ fun ChannelsScreen(
     epoch: Int = 0,
     onOpenDrawer: () -> Unit = {},
     drawerPulse: Int = 0,
+    /** Channel opened last — gets the focus back on return (issue #34). */
+    focusHandle: String? = null,
     viewModel: ChannelsViewModel = viewModel(key = "channels$epoch", factory = ChannelsViewModel.factory),
 ) {
     LaunchedEffect(epoch) { viewModel.load() }
@@ -358,13 +367,22 @@ fun ChannelsScreen(
                         )
                     }
                     item(key = "row-" + group.ownerName) {
+                        // Coming back from a channel page, focus the card we opened
+                        // instead of the very first one (issue #34).
+                        val target = group.channels.indexOfFirst {
+                            it.name + "@" + it.host == focusHandle
+                        }
+                        val isTargetRow = target >= 0
                         ChannelRow(
                             group.channels,
                             onOpenChannel,
                             onOpenDrawer,
                             drawerPulse = drawerPulse,
-                            focused = !focusHandedOut.value &&
+                            focused = !focusHandedOut.value && (
-                                group == viewModel.userRows.firstOrNull(),
+                                if (focusHandle != null) isTargetRow
+                                else group == viewModel.userRows.firstOrNull()
+                            ),
+                            focusIndex = if (isTargetRow) target else 0,
                             onFocused = { focusHandedOut.value = true },
                             stats = { viewModel.stats[it.name + "@" + it.host] },
                             platformName = { viewModel.platformNames[it.host ?: ""] },
@@ -419,6 +437,8 @@ private fun ChannelRow(
     onOpenDrawer: () -> Unit = {},
     drawerPulse: Int = 0,
     focused: Boolean,
+    /** Which card to hand the initial focus to (issue #34). */
+    focusIndex: Int = 0,
     onFocused: () -> Unit = {},
     stats: (VideoChannelDto) -> net.jeena.jtubetv.data.api.ChannelStats?,
     platformName: (VideoChannelDto) -> String?,
@@ -445,17 +465,30 @@ private fun ChannelRow(
         }
     }
     if (focused) {
-        LaunchedEffect(channels.isNotEmpty()) {
+        LaunchedEffect(channels.isNotEmpty(), focusIndex) {
             if (channels.isNotEmpty()) {
-                if (runCatching { focusRequesters[0]?.requestFocus() }.isSuccess) onFocused()
+                val target = focusIndex.coerceIn(0, channels.size - 1)
+                // Bring it on screen first; a card further right isn't composed yet,
+                // so retry until its focus requester is attached (issue #34).
+                if (target > 0) runCatching { rowState.scrollToItem(target) }
+                repeat(8) {
+                    delay(80)
+                    val ok = runCatching { focusRequesters[target]?.requestFocus() }.getOrNull()
+                    if (ok != null) {
+                        onFocused()
+                        return@LaunchedEffect
+                    }
+                }
             }
         }
     }
 
     LazyRow(
         state = rowState,
-        // Land on the last-focused card when moving between rows (issue #29).
+        // Land on the last-focused card when moving between rows (issue #29). No
-        modifier = Modifier.focusRestorer { focusRequesters[focusedIndex.coerceAtLeast(0)] ?: FocusRequester.Default },
+        // custom fallback: a requester whose card has scrolled out of composition
+        // crashed with "FocusRequester is not initialized".
+        modifier = Modifier.focusRestorer(),
         contentPadding = PaddingValues(horizontal = 12.dp),
         horizontalArrangement = Arrangement.spacedBy(4.dp),
     ) {

app/src/main/java/net/jeena/jtubetv/ui/screens/HomeRows.kt

@@ -457,8 +457,10 @@ fun FocusScrollRow(
         state = rowState,
         // Jumping between rows lands on the card this row last had focus on, not
         // the geometrically-nearest one (issue #29): the rows stop shifting
-        // left/right as you move up and down between them.
+        // left/right as you move up and down between them. No custom fallback —
-        modifier = Modifier.focusRestorer { focusRequesters[focusedIndex.coerceAtLeast(0)] ?: FocusRequester.Default },
+        // handing back a requester whose card has scrolled out of composition
+        // crashed with "FocusRequester is not initialized".
+        modifier = Modifier.focusRestorer(),
         contentPadding = PaddingValues(horizontal = 12.dp),
         horizontalArrangement = Arrangement.spacedBy(4.dp),
     ) {

app/src/main/java/net/jeena/jtubetv/ui/screens/HomeScreen.kt

@@ -87,6 +87,16 @@ fun HomeScreen(viewModel: AppViewModel = androidx.lifecycle.viewmodel.compose.vi
     var destination by rememberSaveable { mutableStateOf(Destination.Home) }
     var channelDetails by rememberSaveable { mutableStateOf<String?>(null) } // handle
     var channelName by rememberSaveable { mutableStateOf<String?>(null) }   // display name
+    // Last channel opened from the Channels screen — refocused on return (#34).
+    var lastOpenedChannel by rememberSaveable { mutableStateOf<String?>(null) }
+    // Channels are expensive to assemble, so start that work at app launch rather
+    // than when the view is first opened (issue #32); the view then usually finds
+    // the rows already there, and load() no-ops while fresh.
+    val channelsViewModel: ChannelsViewModel = androidx.lifecycle.viewmodel.compose.viewModel(
+        key = "channels$epoch",
+        factory = ChannelsViewModel.factory,
+    )
+    LaunchedEffect(epoch) { channelsViewModel.load() }
     // NOT saveable: launching the app should never resume a half-watched player session.
     var playingVideo by rememberSaveable { mutableStateOf<String?>(null) }  // shortUUID
     // Non-null while the playing video lives on ANOTHER instance (vidiverse results).
@@ -220,10 +230,16 @@ fun HomeScreen(viewModel: AppViewModel = androidx.lifecycle.viewmodel.compose.vi
                             drawerPulse = drawerPulse,
                         )
                     Destination.Channels -> ChannelsScreen(
-                        onOpenChannel = { handle -> channelDetails = handle },
+                        onOpenChannel = { handle ->
+                            channelDetails = handle
+                            lastOpenedChannel = handle
+                        },
                         epoch = epoch,
                         onOpenDrawer = { drawerOpen = true },
                         drawerPulse = drawerPulse,
+                        // Back from a channel page re-selects it (issue #34).
+                        focusHandle = lastOpenedChannel,
+                        viewModel = channelsViewModel,
                     )
                     Destination.Search ->
                         VideoListScreen(