[georgereade]

Closes #10808

Summary

Sheet is visibly delayed when entering with position="end" / "start" on wide screens, as onEnter scrolls the container a full viewport. Sheets narrower or shorter than the viewport spend most of the animation off screen. Most noticeable on widescreens but reduces dead time in almost all cases (including mobile screens with position="bottom").

Fix

Jump to where the sheet's leading edge meets the viewport before smooth scrolling, so the animation is instant after clicking the trigger.

✅ Pull Request Checklist:

• Included link to corresponding React Spectrum GitHub Issue.
• Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• Filled out test instructions.
• Updated documentation (if it already exists for this component).
• Looked at the Accessibility Practices for this feature - Aria Practices
• I understand every change in this PR and can explain why it's there.
• If AI-assisted, I followed our AI contribution guidance and pointed my assistant at AGENTS.md.

📝 Test Instructions:

Go to the Sheet docs on a widescreen, change position to "end" and observe the delay for the backdrop to fade and sheet to enter. On this branch, run the docs locally yarn start:s2-docs and do the same check, there is now no delay.

current:
https://github.com/user-attachments/assets/04d10da4-f177-4668-a587-8a5cba853580

fix:
https://github.com/user-attachments/assets/0fb27146-d265-4f9b-bc2d-35501c617c4a

Added new tests in Sheet.test.js

🧢 Your Project:

ISM Fantasy Games (Fantasy Premier League)

[reidbarber]

Thanks!

[snowystinger]

tested with reduced motion as well, that's still working as expected