Fix/brackets crashes

[usmanvrtx]

Description

This PR fixes crashes, stale focus updates, and layout instability in the Bracket widget during TV focus navigation, tab changes, scrolling, animated transitions, and dynamic data updates.

It also improves Bracket layout behavior for unequal columns and keeps focus, tab, and resize state synchronized as bracket content changes.

Related Issue

N/A

Type of Change

• Bug fix (non-breaking change that fixes an issue)
• New feature (non-breaking change that adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update
• Refactoring (no functional changes)

What Has Changed

• Improved Bracket focus handling during vertical and horizontal TV navigation.
• Prevented stale focus updates from applying after a newer navigation or transition request.
• Stabilized layout animations, scroll anchoring, and focus transitions.
• Synchronized tab keys and resize scroll controllers when bracket data changes.
• Improved tab selection and focus behavior during horizontal transitions.
• Added handling and regression coverage for unequal column layouts.
• Improved Bracket layout and TV navigation behavior across changing screen dimensions.
• Updated Bracket documentation, TV navigation guidance, schema definitions, and related examples.
• Added and updated widget tests covering Bracket layout, tab selection, scrolling, and repeated focus navigation.

How to Test

1. Run melos bootstrap from the repository root.
2. Run the focused Bracket tests:

   cd modules/bracket
   flutter test

3. Run analysis for the affected modules:

   cd modules/bracket
   flutter analyze
   
   cd ../ensemble
   flutter analyze

4. Open a Bracket screen and verify vertical and horizontal TV navigation, tab changes, scrolling, and focus transitions.
5. Verify Bracket screens with unequal column sizes and changing bracket data.
6. Resize the screen or rotate between supported layouts and verify that content, focus, and scrolling remain stable without crashes.

Screenshots / Videos

Not applicable.

Checklist

• I have run flutter analyze and addressed any new warnings
• I have run flutter test and all tests pass
• I have tested my changes on the relevant platform(s)
• I have updated documentation if needed
• My changes do not introduce new warnings or errors