feat(mobile): harden unread badges and float tabs

AGENTS.md

@@ -218,12 +218,17 @@ Desktop E2E: `cd desktop && pnpm exec playwright test`
 
 See [TESTING.md](TESTING.md) for the full multi-agent E2E guide.
 
-### Desktop Screenshots (Playwright)
+### PR Screenshots
 
 > **Do NOT use `buzz upload`, the relay media endpoint, or any third-party
 > image host for PR screenshots.** Relay media URLs fail through GitHub's camo
-> proxy. Always use `scripts/post-screenshots.sh` — see the `desktop-screenshot`
-> skill for the full workflow.
+> proxy. Always use `scripts/post-screenshots.sh` for PNGs before linking them
+> from a PR body/comment. If you hand-edit PR markdown, run
+> `scripts/check-pr-image-urls.sh <markdown-file>` first to catch relay URLs.
+
+For mobile simulator screenshots, save the PNGs in a local directory and run
+`./scripts/post-screenshots.sh <PR-number> <png-dir>` or use the third argument
+with a markdown template containing `{{filename}}` placeholders.
 
 The desktop app requires the E2E mock bridge to render — it cannot run in a plain
 browser. Use `just desktop-screenshot` to capture screenshots (builds frontend,

desktop/src-tauri/src/managed_agents/screenshot_skill.md

@@ -16,6 +16,12 @@ unreliable and may expose content.
 
 **ALWAYS use `scripts/post-screenshots.sh`** — it hosts PNGs on a per-developer
 git branch with immutable commit-SHA URLs that render correctly on GitHub.
+If you manually compose or edit PR markdown, run
+`scripts/check-pr-image-urls.sh <markdown-file>` before posting. The checker
+fails on Buzz/relay media URLs so broken images are caught locally.
+
+This hosting rule applies to any PNG you want in a PR, including mobile
+simulator screenshots captured outside the desktop Playwright helper.
 
 ## Step 1 — Capture Screenshots
 

mobile/lib/features/channels/channel_detail_page.dart

@@ -64,6 +64,7 @@ int? _channelReadTimestamp({
   if (events != null && events.isNotEmpty) {
     var latest = 0;
     for (final event in events) {
+      if (event.threadReference.parentId != null) continue;
       if (event.createdAt > latest) {
         latest = event.createdAt;
       }
@@ -132,6 +133,9 @@ class ChannelDetailPage extends HookConsumerWidget {
         ref
             .read(readStateProvider.notifier)
             .markContextRead(channel.id, readTimestamp);
+        ref
+            .read(channelsProvider.notifier)
+            .clearObservedUnreadCoveredByRead(channel.id, readTimestamp);
       });
     }, [channel.id, readState.isReady, readTimestamp]);
 

mobile/lib/features/channels/channels_page.dart

@@ -488,6 +488,9 @@ class _SliverChannelsList extends HookConsumerWidget {
                     ref
                         .read(readStateProvider.notifier)
                         .markContextRead(channel.id, ts);
+                    ref
+                        .read(channelsProvider.notifier)
+                        .clearObservedUnreadCoveredByRead(channel.id, ts);
                   }
                 },
               ),
@@ -1104,6 +1107,9 @@ class _ChannelTile extends ConsumerWidget {
                         ref
                             .read(readStateProvider.notifier)
                             .markContextRead(channel.id, ts);
+                        ref
+                            .read(channelsProvider.notifier)
+                            .clearObservedUnreadCoveredByRead(channel.id, ts);
                       } else {
                         ref
                             .read(readStateProvider.notifier)