fix: Input IME enter to complete composition bug

[alexisareyn]

Fix race condition where compositionend fires before onKeyDown handler, causing premature search submission when users press Enter to complete character composition.

This was resolved for the Autosuggest component in : #4182

• Add useIMEComposition hook to track composition state with requestAnimationFrame
• Modify Input to use isComposing() check
• Add comprehensive tests for IME composition scenarios
• Ensure Enter key during composition completion doesn't trigger search

Description

This PR fixes a critical accessibility issue affecting Korean (and other IME) users where pressing Enter to complete character composition would accidentally trigger search submission instead of just completing the character.

Problem: When Korean users type characters like 가 (ga), pressing Enter to complete the character would incorrectly trigger search submission because the browser's compositionend event fires before the onKeyDown handler executes, creating a race condition.

Root Cause: The timing issue meant there was no reliable way to distinguish between "Enter pressed to complete character composition" vs "Enter pressed to trigger search".

Solution: Created a useIMEComposition hook that tracks composition state and uses requestAnimationFrame to maintain the composition flag briefly after compositionend, allowing the onKeyDown handler to correctly identify composition-related Enter keypresses and prevent inappropriate search triggering.

How has this been tested?

Automated Testing:

• Added 13 comprehensive unit tests for the new useIMEComposition hook covering character formation, multiple composition cycles, edge cases, and proper cleanup
• Modified existing autosuggest integration tests to verify IME scenarios
• All tests pass: npm test

Manual Testing:

• Start the dev server: npm start

• Navigate to the autosuggest search page at http://localhost:8080

• Switch to Korean 2-set keyboard input method

• Type Korean characters (e.g., ㄱ + ㅏ to form 가) and press Enter to complete - should NOT trigger search

• Type regular text and press Enter - should trigger search normally

• Run automated tests: npm test

Review checklist

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

Correctness

• [N/A] 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

• [N/A] 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 97.44%. Comparing base (3dcd7e0) to head (16ac3dc).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4338      +/-   ##
==========================================
- Coverage   97.45%   97.44%   -0.01%     
==========================================
  Files         902      902              
  Lines       26468    26474       +6     
  Branches     9540     9542       +2     
==========================================
+ Hits        25794    25798       +4     
- Misses        631      633       +2     
  Partials       43       43              

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[alexisareyn]

Update:

1. I removed the integration test I originally included. I forgot that when making fix: resolve IME enter to complete composition bug #4182 I was not able to add one. Browser automations cannot simulate real IME composition events b/c IME lives at OS level which means that we cannot simulate the IME events on a 2 set keyboard.

2. The failing tests in /src\/app-layout\/__integ__\/app-layout-error-boundaries.test.ts fail locally on main for me - has this issue been seen before?

3. As for the measure failure, Unhandled error: HttpError: Resource not accessible by integration , I was not super sure what to do about this. Copilot said "The error "Resource not accessible by integration" happened during a step using actions/github-script@v7 to report failure in the bundle size workflow. This is usually caused by missing or incorrect GitHub token permissions.". @georgylobko do you know how to resolve this?

[georgylobko]

1. Got it, so I assume pages/input/korean-ime.page.tsx isn't needed then?

2. No, this is a new one, and from what I can see, the tests are passing in the pipeline

3. No worries, we don't run certain workflows for external contributions