fix(emoji-board): cancel in-flight gif searches and debounce timers

[eleboucher]

Description

gif search never aborted its requests so a slow response could land after you closed the picker or typed something newer and overwrite the results. now aborts and ignores stale ones.

useDebounce also never cleared its timer on unmount, now it does and returns a cancel().

Fixes #

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

AI disclosure:

• Partially AI assisted (clarify which code was AI assisted and briefly explain what it does).
• Fully AI generated (explain what all the generated code does in moderate detail).

[github-actions]

Deploying with    Cloudflare Workers

Status	Preview URL	Commit	Alias	Updated (UTC)
✅ Deployment successful!	https://pr-1562-sable.raspy-dream-bb1d.workers.dev	307757e	pr-1562	Sat, 01 Aug 2026 15:40:37 GMT