Add native-style mobile action menus

[klopez4212]

Summary

• present lifted message previews with native iOS actions and a matching curved Android action surface
• keep the existing emoji reaction tray and add the same long-press treatment to Activity rows
• use native iOS filter menus where supported while retaining Flutter fallbacks on other platforms

Why

Message and Activity actions previously relied on sheets or disconnected menus. This gives both platforms a compact, contextual presentation while preserving existing action and reaction behavior.

Validation

• just mobile-check
• full Flutter test suite (1,285 tests)
• focused message and Activity widget tests (153 tests)
• native iOS RunnerTests suite (29 tests)
• installed and reviewed on a physical iPhone and Pixel 10

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Retain the snapshot through the reverse transition

With animations enabled, the future returned by showGeneralDialog completes when Navigator.pop starts, while _MessageActionsPopover remains mounted and paints during the 240 ms reverse transition. Disposing snapshot here—and restoring the hidden source in the next line—can make those remaining frames render a disposed image or show both copies of the message. Defer disposal and onPopoverDismissed until the route unmounts or reaches AnimationStatus.dismissed, as the new Activity popover already does; the reaction-only iOS and Android paths contain the same lifecycle error.

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[chatgpt-codex-connector]

Keep the action menu above the keyboard

When the composer keyboard remains open and the user long-presses a visible message, this layout treats the obscured keyboard area as available because safeBottom subtracts only system padding. The combined tray, preview, and action surface are therefore centered partly behind the keyboard, which can hide lower actions and make them untappable. Account for mediaQuery.viewInsets.bottom (and the top inset) here, as _MessageReactionPopover already does.

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