Accessibility issue: Toolbar dropdown reading order broken for screen readers

[thassio-vinicius]

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Flutter Quill Version

11.4.2

Steps to Reproduce

1. Create a Flutter app with flutter_quill and a QuillSimpleToolbar.
2. Include a QuillToolbarSelectHeaderStyleDropdownButtonOptions in the toolbar configuration.
3. Enable TalkBack (Android) or VoiceOver (iOS).
4. Navigate through the toolbar items using accessibility gestures or keyboard focus.
5. Observe that the header style dropdown is skipped entirely until navigating backward, disrupting the logical reading order of toolbar items.

Expected results

1. The toolbar items are read sequentially in the order they appear in the UI.
2. The header style dropdown is read and accessible in its correct position between other toolbar items.

Actual results

1. The header style dropdown appears to be read first, regardless of its position in the toolbar.
2. The user must navigate back to access it.
3. Screen readers may skip other toolbar elements if they rely on the current behavior.

Additional Context

Modifying the dropdown itself is difficult because QuillToolbarSelectHeaderStyleDropdownButtonOptions does not provide a direct semantic label or child semantics control.