Header grows a flex-1 column between the brand and the user menu.
Existing Shell tests remain green (the search input has no impact on
nav/menu behavior).
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.
Wraps the existing link in a relative container; adds an absolutely
positioned + button. On click stops propagation, fetches /api/albums/:id
once, and feeds tracks into enqueueTracks.
Outer <button> becomes <div role="button" tabindex="0"> with keyboard
handlers (Enter/Space) so a real <button> for + queue can nest without
invalid HTML. New optional onPlay prop overrides the default
playQueue(tracks, index); used by the search Tracks section to call
playRadio(track.id) instead. + queue button calls enqueueTrack and
stops propagation so the row click does not fire.
Grid grows to 3 rows (auto / 1fr / auto); PlayerBar spans both columns
in the last row, rendering only when player.current is defined so the
row collapses before first play.
TrackRow becomes a <button> that dispatches playQueue(tracks, index).
Album page supplies the full track list + each index so the rest of
the album enqueues automatically when the user clicks a track.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>