fix: Fixes a bug when pointer d&d transition crashes when pressing Escape

[pan-kot]

Description

We have two drastically different types of d&d transition: pointer-based and keyboard-based. Due to async nature of events, there was a bug where the pointer-based transition crashed when user pressed Escape. It happened because:

1. User starts pointer-based d&d transition (moves or resizes an item, but w/o commit);
2. User presses Escape (or Space, Enter) - the keyboard handler submits/discards the transition;
3. User moves cursor a little - the onPointerMove handler is still there, it attempts to update the transition that no longer exists, which leads to a crash.

Besides, pressing arrow keys while the pointer-based transition was in progress led to unexpected results, too. The solution is to disallow keyboard input while pointer-based d&d is engaged by immediately cancelling the transition in this case.

I additionally refactored the code a little so that the global handlers are injected in a better predictable manner, so instead of relying on whether the handlers are present - we rely on a ref that tells us whether a transition is engaged.

Rel: AWSUI-61155, similar to: #367

The change also fixes AWSUI-61157. Before, when the right-click (reproducible with a mouse, but not with trackpad) was made during a pointer-based d&d operation, the transition was stuck because the related pointer-up was removed. This is no longer the case.

Before:

Screen.Recording.2025-08-26.at.13.57.00.mov

After:

Screen.Recording.2025-08-26.at.13.57.40.mov

How has this been tested?

• Added new functional test as a regression

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md.
• Changes do not include unsupported browser features, see CONTRIBUTING.md.
• Changes were manually tested for accessibility, see accessibility guidelines.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function.

Testing

• Changes are covered with new/existing unit tests?
• Changes are covered with new/existing integration tests?

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.39%. Comparing base (5ba94ef) to head (25497ab).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #368      +/-   ##
==========================================
+ Coverage   94.97%   95.39%   +0.42%     
==========================================
  Files          67       67              
  Lines        3263     3282      +19     
  Branches      699      707       +8     
==========================================
+ Hits         3099     3131      +32     
+ Misses        164      151      -13     

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[pan-kot]

@johannes-weber I also tested the board manually by mixing different d&d interactions, including pointer-based, UAP-based, keyboard-based. That is to ensure it is not possible to disengage the global listeners w/o submitting or cancelling the respective transition. If that is the case - the moved/resized item will be stuck in mid-air, unable to commit. Please do a round of manual testing too, just to be sure.

[johannes-weber]

Great improvement! It did not make sense having the global event listeners attached on every board item!

[johannes-weber]

I did manual testing and was not able to crash it with a mix of D&D and keyboard interactions. Tested with a trackpad, I don't have a external mouse available.
LGTM!