Mobile: add anchored reaction popover

[klopez4212]

Summary

• replace reaction-only mobile sheets with an anchored long-press popover
• add haptics, a dimmed frosted spotlight, and a spring-staggered reaction tray
• preserve the full action sheet whenever other message actions are available
• keep existing reaction pills outside the spotlight and make long press reliable across nested content

Testing

• flutter analyze
• flutter test (1,248 tests)
• signed iPhone release build installed and launched

[klopez4212]

🤖

Emoji-only action

A reaction-only system event opens the anchored frosted popover.

Full action sheet fallback

A regular message keeps the existing sheet when more actions are available.

[chatgpt-codex-connector]

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Reviewed commit: fca0644798

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[chatgpt-codex-connector]

Let descendant long presses win

When a user holds an existing reaction pill, its own GestureDetector invokes showReactionDetailSheet (reaction_row.dart:131), but this independent timer can also reach recognize() because it does not participate in the gesture arena. At the shared long-press deadline the child may already have accepted before cancelPointer runs, causing both modal routes to be pushed and the message reaction picker to cover the reactor-detail sheet. Use a gesture-arena-aware recognizer or otherwise suppress the parent callback when a descendant handles the long press.

Useful? React with 👍 / 👎.

[chatgpt-codex-connector]

Keep only one public widget in this file

This file introduces both MessageLongPressInkWell and MessageLongPressRegion as public widgets, contrary to the mobile convention requiring one public widget per file. Make the implementation widget private or move it to a sibling file so the public surface remains composable and file ownership stays unambiguous.

AGENTS.md reference: AGENTS.md:L545-L547

Useful? React with 👍 / 👎.