v0.7.0: startup speed — the 21k-track library stops freezing

Three reported symptoms, one shape: every operation was whole-library,
whole-file, on the Qt main thread. Measured on the real library (21,482
tracks, 506 playlists, 15 MB library.json).

The track table sorted through a QSortFilterProxyModel, which asks data()
for a value on every comparison — 580k Python round trips, 8.5 s per table
load, paid again on every reload. TrackTableModel now keeps _tracks in
canonical (playlist) order plus an _order index list and sorts a key list
computed once per track. Nothing used the proxy's filtering. Sorting by #
is the identity order, so "source row" still means "playlist position" for
drag-reorder. 8.5 s -> 0.13 s; MainWindow() 18.1 s -> 0.79 s.

Smart rules compile to closures once per evaluate() instead of being
re-dispatched per track — the operator lookup, casefolding the query and
parsing the rule's own date constants all leave the 21k-iteration loop
(_match_date was re-parsing its own constant 21,482 times per rule).
Verified identical membership against the old evaluator on all 20 real
smart playlists. 2.54 s -> 0.72 s, and it now runs after the first paint.

Also: _reconcile_track skips two to_dict() round trips per unchanged track
(MERGEABLE_FIELDS in the resolver is the single source of truth for what a
merge touches); no git subprocess on the startup path (Updater.enabled is
probed lazily on the background thread, version-button tooltip deferred);
and .resolved/ is pruned to the newest 10 snapshots — it had reached 1.7 GB
across 73 snapshots inside the Syncthing share.

Time to interactive window ~15 s -> 3.2 s. The mid-session freeze when
Syncthing delivers a change — a full reload + recompute + table rebuild
with the window already on screen, which is what GNOME was offering to
force-quit — ~16 s -> 3.8 s.

The merge rework itself (playlist ordering, per-machine play journal,
quieting the dialog) is queued in TASKS.md as Round 36.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/test_round17.py

@@ -330,7 +330,7 @@ class TestRatingClicks:
         emitted = []
         view.rating_edited.connect(lambda tid, r: emitted.append((tid, r)))
         col = view.model_.fields.index("rating")
-        rect = view.visualRect(view.proxy.index(0, col))
+        rect = view.visualRect(view.model_.index(0, col))
         slot_w = rating_slot_width(QFontMetrics(view.font()))
         # Click the 4th slot → 80.
         x = rect.left() + RATING_LEFT_PAD + int(slot_w * 3.5)
@@ -356,10 +356,10 @@ class TestRatingClicks:
         track = Track(track_id=1, name="A", rating=40)
         view = self._view(qapp, [track])
         col = view.model_.fields.index("rating")
-        index = view.proxy.index(0, col)
+        index = view.model_.index(0, col)
         view._set_rating_hover(index)
         assert view.is_rating_hovered(index)
-        assert not view.is_rating_hovered(view.proxy.index(0, 0))
+        assert not view.is_rating_hovered(view.model_.index(0, 0))
         view._set_rating_hover(None)
         assert not view.is_rating_hovered(index)