longform: fix opening midway instead of at top

The scroll_to_event function defaults to anchor: .bottom, which positions
the selected event at the bottom of the viewport. For longform notes,
this causes the article to open midway or at the bottom instead of the
top where the title is.

Changed the initial scroll anchor to .top only for longform articles
(kind 30023), preserving the existing .bottom behavior for regular notes
which keeps parent context visible in reply threads.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Closes: https://github.com/damus-io/damus/issues/2481
Closes: https://github.com/damus-io/damus/pull/3488
Changelog-Fixed: Longform articles now open at the top instead of midway through
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
Tested-by: William Casarin <jb55@jb55.com>
Signed-off-by: alltheseas
Signed-off-by: William Casarin <jb55@jb55.com>

damus/Features/Chat/ChatroomThreadView.swift

@@ -383,7 +383,10 @@ struct ChatroomThreadView: View {
             }
             .onAppear() {
                 thread.subscribe()
-                scroll_to_event(scroller: scroller, id: thread.selected_event.id, delay: 0.1, animate: false)
+                // Use .top anchor for longform articles so they open at the title,
+                // keep .bottom for regular notes to preserve parent context visibility
+                let anchor: UnitPoint = thread.selected_event.known_kind == .longform ? .top : .bottom
+                scroll_to_event(scroller: scroller, id: thread.selected_event.id, delay: 0.1, animate: false, anchor: anchor)
                 // Ensure chrome is visible when view appears (handles interrupted transitions)
                 if isLongformEvent {
                     chromeHidden = false