fix(mobile): keep latest messages above composer

mobile/lib/features/channels/channel_detail_page/message_list.dart

@@ -155,6 +155,13 @@ class _MessageList extends HookConsumerWidget {
           : displayEntries.length - 1 - chronologicalIndex;
     }
 
+    double latestAlignment() {
+      final viewportHeight = context.size?.height ?? 0;
+      return viewportHeight > 0
+          ? (composerBottomInset / viewportHeight).clamp(0.0, 1.0).toDouble()
+          : 0.0;
+    }
+
     Future<void> scrollToLatest() async {
       if (!itemScrollController.isAttached || isAutoScrolling.value) return;
       followsLatest.value = true;
@@ -163,6 +170,7 @@ class _MessageList extends HookConsumerWidget {
       try {
         await itemScrollController.scrollTo(
           index: 0,
+          alignment: latestAlignment(),
           duration: const Duration(milliseconds: 220),
           curve: Curves.easeOutCubic,
         );
@@ -199,12 +207,15 @@ class _MessageList extends HookConsumerWidget {
     }
 
     bool latestIsAtBoundary() {
-      // In this reversed list, item 0's leading edge is the bottom boundary.
-      // Being merely visible is not enough: a user who has pulled a tall
-      // newest row away from the boundary must not snap back on live updates.
+      // In this reversed list, item 0's leading edge is the visible bottom
+      // boundary above the composer. Being merely visible is not enough: a
+      // user who has pulled a tall newest row away from that boundary must not
+      // snap back on live updates.
+      final boundary = latestAlignment();
       return itemPositionsListener.itemPositions.value.any(
         (position) =>
-            position.index == 0 && position.itemLeadingEdge.abs() < 0.01,
+            position.index == 0 &&
+            (position.itemLeadingEdge - boundary).abs() < 0.01,
       );
     }
 

mobile/test/features/channels/channel_detail_page_test.dart

@@ -1811,7 +1811,7 @@ void main() {
         expect(latestMessage, findsOneWidget);
         expect(
           tester.getBottomLeft(latestMessage).dy,
-          lessThanOrEqualTo(tester.getTopLeft(composerDock).dy + 1),
+          closeTo(tester.getTopLeft(composerDock).dy, 1),
         );
 
         await tester.tap(find.text('Message #general'));
@@ -1823,7 +1823,7 @@ void main() {
         );
         expect(
           tester.getBottomLeft(latestMessage).dy,
-          lessThanOrEqualTo(tester.getTopLeft(composerDock).dy + 1),
+          closeTo(tester.getTopLeft(composerDock).dy, 1),
         );
         expect(
           find.byKey(const ValueKey('channel-jump-to-latest')),
@@ -1836,7 +1836,57 @@ void main() {
         expect(latestMessage, findsOneWidget);
         expect(
           tester.getBottomLeft(latestMessage).dy,
-          lessThanOrEqualTo(tester.getTopLeft(composerDock).dy + 1),
+          closeTo(tester.getTopLeft(composerDock).dy, 1),
+        );
+        expect(
+          find.byKey(const ValueKey('channel-jump-to-latest')),
+          findsNothing,
+        );
+      },
+    );
+
+    testWidgets(
+      'keeps a short followed tail flush through composer resize',
+      (tester) async {
+        tester.view.physicalSize = const Size(400, 800);
+        tester.view.devicePixelRatio = 1;
+        addTearDown(tester.view.resetPhysicalSize);
+        addTearDown(tester.view.resetDevicePixelRatio);
+        addTearDown(tester.view.reset);
+
+        final messages = [
+          for (var i = 0; i < 3; i++)
+            _textMsg(
+              id: 'msg$i',
+              pubkey: 'alice',
+              content: 'Message $i',
+              createdAt: 1000 + i,
+            ),
+        ];
+
+        await tester.pumpWidget(
+          _buildTestable(
+            messages: messages,
+            users: const {
+              'alice': UserProfile(pubkey: 'alice', displayName: 'Alice'),
+            },
+          ),
+        );
+        await tester.pumpAndSettle();
+
+        final latestMessage = find.byKey(
+          const ValueKey('channel-message-group-msg2'),
+        );
+        final composerDock = find.byKey(
+          const ValueKey('channel-composer-dock'),
+        );
+
+        await tester.tap(find.text('Message #general'));
+        await tester.pumpAndSettle();
+
+        expect(
+          tester.getBottomLeft(latestMessage).dy,
+          closeTo(tester.getTopLeft(composerDock).dy, 1),
         );
         expect(
           find.byKey(const ValueKey('channel-jump-to-latest')),
@@ -1990,6 +2040,18 @@ void main() {
       await tester.pumpAndSettle();
 
       expect(findRichText('Newest live update'), findsOneWidget);
+      final latestMessage = find.byKey(
+        const ValueKey('channel-message-group-newest'),
+      );
+      final composerDock = find.byKey(const ValueKey('channel-composer-dock'));
+      expect(
+        tester.getBottomLeft(latestMessage).dy,
+        closeTo(tester.getTopLeft(composerDock).dy, 1),
+      );
+      expect(
+        find.byKey(const ValueKey('channel-jump-to-latest')),
+        findsNothing,
+      );
     });
 
     testWidgets(