feat(track-list): show Album by default, and search smart playlists

H-15: the default columns were track, artist and duration, so a library
manager with duplicate detection could not tell its own duplicate
fixtures apart by eye. Album is a default now, in Go and in the
frontend fallback — both, because a fresh install persists the Go list
and the UI renders the TS one until the config arrives.

It does not deliver the finding's stated benefit, and that is worth
recording: the three `Tideline / Aurora Fields / 00:06` rows are
duplicates of the same album, so they read identically with an Album
column too. What tells them apart is the duplicate-detection feature or
a file path column, not this. Album is still the right default for
every other row in the list.

smart-playlist-details joins search-store's scope map. Checked before
adding, as asked: it reads searchCtrl.term in getVisibleTracks and
prints the term in the page, so the header box was disabled and
unlabelled on a view that filters as you type — the fix is a scope
entry, not a disabled state with a reason.

frontend/test/stores/view-stores.test.ts

@@ -54,6 +54,10 @@ describe('search store', () => {
       'albums',
       'playlists',
       'playlist-details',
+      // A detail view that filters on the term has to be in the map:
+      // this one was not, so the box was disabled and unlabelled on a
+      // page that narrowed its list as you typed.
+      'smart-playlist-details',
       'artists',
       'genres',
     ].map((view) => {