Materialize the trash — store, undo, and the container universe

Phase 2 swaps every consumer: Liveness and its ancestor walk are gone,
replaced by ItemContainer — a UUID set plus the container side it
lives on, presence the whole test, one selection boundary instead of
the old liveness law. Deletion stages by place: board cards move to
the trash at a store-minted head rank, trash-side delete is permanent
behind its confirmation, Delete Immediately skips the trash from
anywhere, lane delete captures the subtree and removes the folder.
Restore has no method at all — moveCards resolves members in either
container, so drag-out and cut-paste are the ordinary moves 13 calls
them, registering ordinary Move steps. The delete inverse moves the
card back to its captured lane and rank; redo replays the captured
trash rank, a value the gesture actually wrote; lane undo recreates
the subtree byte-faithfully in session. Purges register nothing —
where 13's trash section contradicts its own Rules on that, Rules
wins, filed for ruling. Staleness collapsed to present-or-absent: a
container is a path, so a foreign restore fails the delete step's
expectation structurally. Legacy tombstones migrate on the loose-file
tail hook, cards oldest-first so minting above top reproduces the
retired newest-first column, lanes returning live, one folded loss
row naming both directions. Put Back, restoreByDrag,
receiveRestoredCards, TrashEntry, and the kind machinery are deleted;
the trash column renders the container correctly with its full face
rework left to phase 3.

Claude-Session: https://claude.ai/code/session_01SR4XGjmBE16ZUYWpfFHXwY

Kanban/UI/Board/MarqueeSession.swift

@@ -30,7 +30,7 @@ final class MarqueeSession {
     private(set) var current: CGPoint = .zero
 
     /// The side of the live/trash boundary this band selects on, frozen at `begin`.
-    private(set) var side: Liveness = .live
+    private(set) var container: ItemContainer = .board
 
     /// How far the pointer must travel before a drag on empty space becomes a band. Larger than the
     /// lane header's threshold because this gesture arms on *any* empty surface, and a click that
@@ -51,10 +51,10 @@ final class MarqueeSession {
         )
     }
 
-    func begin(at point: CGPoint, side: Liveness) {
+    func begin(at point: CGPoint, in container: ItemContainer) {
         origin = point
         current = point
-        self.side = side
+        self.container = container
     }
 
     func update(to point: CGPoint) {
@@ -81,9 +81,9 @@ final class MarqueeSession {
 /// is on screen. It is also what makes the band correct for free across a lane resize, a reorder in
 /// flight, and a foreign reload — the frames simply re-register.
 ///
-/// **Lanes are never registered.** The band selects cards, and trash rows on the trash side; a lane
-/// has no entry here at all, which is 04-interactions.md § Selection's "click-drag rubber-bands
-/// across lanes" made structural rather than filtered.
+/// **Lanes are never registered.** The band selects cards — board cards or trash cards; a lane has
+/// no entry here at all, which is 04-interactions.md § Selection's "click-drag rubber-bands across
+/// lanes" made structural rather than filtered.
 ///
 /// It is also the **begin guard's** universe: a drag that starts inside a registered frame belongs
 /// to that item's own gesture (a card drag, a drag out of the trash), never to the band. Deciding