import: the whole feature, and releases put back together

Everything the import grew over the last week, landing in one go — the
window, the picker, the audition pen, apply, and the review that stands
between them.

The fold is the new part. A release filed as a container of parts arrived
as N albums, because the scan groups audio by its immediate parent and the
container holds none of its own: Analord's eleven volumes were eleven
records, and six more releases split the same way. Records now fold into
the release above them, and apply is handed an explicit part list — never a
recursive walk, which is what let one stray file swallow 288 descendants
and duplicate 9 GB.

Where releases live is read off the collection rather than assumed, so a
genre-nested library moves the answer instead of breaking; below a dominant
majority at one depth the pass refuses entirely, because no folding beats
wrong folding. Three vetoes independent of depth catch a misread level.
Every fold is listed in the review with a way out.

research/import/fold-audit.mjs imports the shipping module, so the audited
code is the running code: 9 folds, 0 swallows across four library shapes,
and none of the 148 artist folders touched. It was that harness that killed
the tempting version of this rule — matching a part against its container
folded 40 artist folders, Mac Demarco's 8 albums into one, because album
folders carry the artist's name.

The regression test found a live bug on the way: parts number from 01 each,
so flattening two discs collided, and "same name, same size" read the
second file as already-imported and dropped it while still counting it.
That reuse now also requires that this run has not already written the
path.

Also here: the picker's accent crossfades between records instead of
cutting through the app's blue (ownership moved to the window, which
survives the per-record re-key), the fullscreen viewer wears the album's
accent instead of the one it left behind in the portal, Skip defers a
record without deciding it, and Keep mine is gone — with the cards picked
field by field it was Next under another name.

src/App.svelte

@@ -4,6 +4,7 @@
     import PlayerBar from "./components/PlayerBar.svelte";
     import NowPlaying from "./components/NowPlaying.svelte";
     import ArtworkViewer from "./components/ArtworkViewer.svelte";
+    import ImportWindow from "./components/ImportWindow.svelte";
     import LoginModal from "./components/LoginModal.svelte";
     import PreviewOverlay from "./components/PreviewOverlay.svelte";
     import DebugOverlay from "./components/DebugOverlay.svelte";
@@ -21,6 +22,7 @@
     import CatalogAlbum from "./views/CatalogAlbum.svelte";
     import CatalogDiscography from "./views/CatalogDiscography.svelte";
     import FollowToast from "./components/FollowToast.svelte";
+    import ImportToast from "./components/ImportToast.svelte";
     import {
         ui,
         initEvents,
@@ -122,8 +124,10 @@
     <NowPlaying />
     <PlayerBar />
     <FollowToast />
+    <ImportToast />
     <PreviewOverlay />
     <ArtworkViewer />
+    <ImportWindow />
     <LoginModal />
     <DebugOverlay />
 </div>