fix: clear input function in Repository searchbox

[bittoby]

Summary

Fixes the X (clear) button in the search input on /repositories. Previously, clicking X would clear the field for a single frame and then the previous search term reappeared, with ?search=… immediately restored in the URL. The button is now a real no-op-free clear: input empties, URL param is removed, full list shows.

Root cause was a callback-identity cascade in DebouncedSearchInput:

• React Router 6's setSearchParams is rebuilt on every URL change, so any callback derived from it (setFilter → handleSearchChange → the onDebouncedChange prop) gets a new reference per URL update.
• DebouncedSearchInput's fire-effect had onDebouncedChange in its dep array, so it re-ran with the stale debounced value the moment the URL changed — re-applying the old search term right after the clear.

Fix uses the latest-ref pattern in src/components/common/DebouncedSearchInput.tsx: the fire-effect now depends only on debounced, while the callback is read from a ref kept in sync via a separate effect. This fixes the bug at the source and protects every other caller (IssuesList, RepositoryPRsTable, RepositoryCodeBrowser, LanguageWeightsTable, MinerPRsTable, MinerOpenDiscoveryIssuesByRepo, WatchlistPage) from the same trap.

Related Issues

Fixes #1282

Type of Change

• Bug fix
• New feature
• Refactor
• Documentation
• Other (describe below)

Screenshots

Before — clicking X briefly clears the input, then git reappears and ?search=git is restored:

before.webm

After — clicking X clears the input and removes ?search= from the URL:

after.webm

Checklist

• New components are modularized/separated where sensible
• Uses predefined theme (e.g. no hardcoded colors)
• Responsive/mobile checked
• Tested against the test API
• npm run format and npm run lint:fix have been run
• npm run build passes
• Screenshots included for any UI/visual changes