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-tauri/src/lib.rs

@@ -3,6 +3,7 @@ mod config;
 mod cover_logo;
 mod diagnostics;
 mod hero_crop;
+mod import;
 mod hero_detector;
 mod loudness;
 mod pipeline;
@@ -99,6 +100,19 @@ pub fn run() {
             commands::add_to_playlist,
             commands::remove_from_playlist,
             commands::catalog_search,
+            import::import_scan,
+            import::import_session_get,
+            import::import_session_set,
+            import::import_session_clear,
+            import::import_get_dest,
+            import::import_set_dest,
+            import::import_apply,
+            import::import_identify,
+            import::import_cover_report,
+            import::import_local_art,
+            import::import_audition,
+            import::import_probe_file,
+            pipeline::rescan_library,
             commands::catalog_artist,
             commands::catalog_artist_art,
             commands::catalog_artist_logos,