Improve Cupertino Sheet Scroll Behavior

[9AZX]

Improve Cupertino Sheet Scroll Behavior

Description

This PR addresses an issue with the Sheet widget where unintended overscroll at the top was causing usability problems. While this solution doesn't perfectly replicate native iOS behavior, it provides a quick win to make the sheet more usable and prevent content expansion issues.

Changes

• Adjusted applyBoundaryConditions method to clamp the scroll position at the top

How Has This Been Tested?

• Manual testing with various scroll scenarios
• Verified that the sheet stops correctly at the top position

Related Issues

Partially addresses:

• 345

• 298

[jamesblasco]

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