Resolve the second design-review batch and drop the face carousel

Rulings written in place: the drop settle yields to the system drag session
(fly-to-slot deferred to WISHLIST #7) and the held proposal's home is the
app-wide DragSession — rendering the arrangement means rendering the card at
release (03, 02); folder drops refuse at hover with loss-row reporting, created
cards land positionally, N shadows, header resolves topmost, shadow-only
feedback (04); the banner vocabulary gains the warning-tone loss row class
(02); all user-initiated creation clears the search (04); loose files beside a
card's index.md relocate into attachments/ with notice — files-only carve-out,
paste normalizes at the boundary, the agent guide teaches it (01, 04, 08);
dropping a card on the shown trash deletes it, shadow pinned topmost (04);
query-emptied lanes keep their slot, the out-transition stays reachable, an
open rename survives the filter, pasteboard staleness accepted (04).

The face carousel does not carry over: the pathfinder's selection-keyed dual
presentation proved undesirable — one presentation per card, selection changes
styling never geometry; the attachment chip and the card window are the whole
media story (03, 01, 10, 11; the same-day carousel settlements superseded on
their Resolved cards).

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

WISHLIST.md

@@ -27,3 +27,7 @@ Per-lane commit trail, the lane sibling of the card History section. Undecided w
 ### 6. EchoLedger-synthesized foreign undo (base edition)
 
 Narrow base Lanework's honest gap vs Pro — foreign/agent edits aren't ⌘Z-able without git (DESIGN/13-native-undo.md ▸ Out of scope). The EchoLedger already classifies every foreign diff for announcements; it could synthesize inverse operations and push foreign steps onto the native stack, making an agent's edit undoable in base too. Real design needed: ordering against app steps, attribution in menu titles, user expectations when undoing work they didn't do, interaction with the staleness rules.
+
+### 7. Custom fly-to-slot drop animation
+
+Drags run as system `NSItemProvider` sessions (cross-board transfer, the copy badge), so a successful drop's replica gets AppKit's brief fade — not the fly-to-slot settle DESIGN/03 originally imagined; 03 resettled the drop as the board's (the held overlay renders the arrangement instantly at release). Reclaiming the literal fly-to-slot needs an `NSDraggingSession` bridge: mask the system fade, fly a shadow-window replica to the slot frame, hide the landed item during flight — a compositing dance that must stay correct across masonry reflows and multi-item drags. Fund only if the system fade ever reads as cheap in practice.