[Bug] iOS: composer long-press copy/paste menu flickers continuously, menu unusable #5226

Summary

On the Buzz iOS app, long-pressing the message composer input field to bring up the copy/paste (edit) menu causes the menu to flicker continuously — it hides and immediately reopens in a loop, making it impossible to tap any menu item (Copy / Paste / Select All). The composer becomes effectively unusable for text editing.

Environment

• Buzz iOS app (Flutter mobile client; mobile/pubspec.yaml — Dart SDK ^3.11.4, pubspec.lock pins Flutter >=3.38.4)
• iOS 16+ (System Context Menu path)
• Repro: long-press (or tap after long-press) inside the message composer input field; menu flickers every time

Root cause analysis

The mobile composer passes a custom contextMenuBuilder (mobile/lib/features/channels/compose_bar/compose_bar_widget.dart:914) that returns SystemContextMenu.editableText on iOS (compose_bar_widget.dart:638-650). Using the iOS System Context Menu is exactly the configuration that triggers a known, still-unfixed Flutter framework bug where the menu hides and immediately reopens (flicker):

• flutter/flutter #168743 (open): "[iOS] Tapping selection to toggle the toolbar doesn't work when using system context menu" — system and Flutter handle the toggle simultaneously
• flutter/flutter #169835 (closed as duplicate of #168743): "[iOS] TextField context menu flickers (hides and reopens) on subsequent single tap" — symptom matches this report verbatim
• flutter/flutter #173489 (open): triple-tap flicker variant
• Fix PR flutter/flutter #169720 (toggleToolbar debounce) and its API split PR #174890 were both closed without merge — upstream remains unfixed

Suggested fix directions (app side)

1. Debounce the toolbar toggle (mirror the upstream proposal): ignore a toggle within ~100ms of the previous hide.
2. Or fall back to Flutter's built-in AdaptiveTextSelectionToolbar.buttonItems on iOS until the framework fix lands.
3. Note: the composer also injects a custom "Paste Image" item gated on clipboardHasImage (compose_bar_widget.dart:641-654); it is refreshed only on focus/resume, so it is not the flicker driver, but any future work on this menu should keep that item's state stable while the menu is open.