Realign code with the 2026-07-31 rulings

The trash sorts by modified descending — the arrival rank mint retires
(Ranks.isOrderedForTrash one comparator, loader + merged order agree;
the legacy deleted: migration stamps modified from the tombstone
timestamp where parseable; delete undo steps validate existence-only;
agent guide v8). Trash selection goes kind-blind — ranges, marquee,
Select All, and the successor walk sweep both kinds; the guard moves to
the exits (mixed-payload drop refusal, copy/cut validation). The copy
stamping preflight widens back to comment depth (load-scoped posture —
the board always loads, the gesture refuses whole). Fixes a latent
no-op: trashed-lane drag restore never fired (DragSession.beginLanes
hard-coded the board container).

2403 tests in 413 suites green.

Claude-Session: https://claude.ai/code/session_01CqjXB7ASoWtbyoGod68k97

KanbanTests/CardWindowFateTests.swift

@@ -90,9 +90,7 @@ struct CardWindowFateTests {
     func aLaneTrashedDismissesItsCards() throws {
         let fixture = try makeBoard()
         defer { fixture.tearDown() }
-        try BoardWriter.deleteLaneToTrash(
-            at: fixture.url(Ident.lane1), inBoard: fixture.root, order: -1024
-        )
+        try BoardWriter.deleteLaneToTrash(at: fixture.url(Ident.lane1), inBoard: fixture.root)
         let snapshot = try BoardLoader.load(boardRoot: fixture.root).model
 
         #expect(snapshot.trashedLanes.map(\.id.rawValue) == [Ident.lane1])