251d165e0b
Pre-fills from page.url.searchParams.get('q'); typing debounces 250ms
then goto('/search?q=…'); first nav from elsewhere pushes, subsequent
typing on /search replaces. Empty input on /search drops the param.
Escape clears the input. URL → value re-sync via \$effect uses
untrack() on the value comparison so it doesn't loop with typing.