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media story (03, 01, 10, 11; the same-day carousel settlements superseded on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

DESIGN/11-command-nexus.md

@@ -77,7 +77,7 @@ All board grammar keys are inert while a title editor is focused, and menu dispa
 - **Drag & drop — the locality model** (04): within-board move / cross-board copy; **⌥ always forces copy, ⌘ always forces move**; multi-drag; lane header is the lane drag surface; drag-to-restore from the trash.
 - **Lane edge drag** (03 ▸ Lane): window-growing resize between integer widths — the one width control that moves the window.
 - **Finder file drops** (04): onto a card = attach; onto lane empty space = one card per file; anywhere on the card window = attach (05's payload-split precedence).
-- **Preview** (05): task-list checkbox toggle (the one interactive exception), link opens, text selection; carousel paging on the card face (03). **In-content controls aren't P-only** (settled): checkboxes and links are real controls in the focus/accessibility tree, so Full Keyboard Access + Space and VO-Space reach them (05 ▸ Task-list checkboxes) — content rides the system focus model rather than earning command rows; "a command absent here doesn't exist" scopes to commands, not content.
+- **Preview** (05): task-list checkbox toggle (the one interactive exception), link opens, text selection. **In-content controls aren't P-only** (settled): checkboxes and links are real controls in the focus/accessibility tree, so Full Keyboard Access + Space and VO-Space reach them (05 ▸ Task-list checkboxes) — content rides the system focus model rather than earning command rows; "a command absent here doesn't exist" scopes to commands, not content.
 - **Lane header new-card button** (03, labeled "New card in ⟨lane⟩" — 10): creates in **the button's lane**, appended at the bottom — the click names its target, overriding 04's selection-derived ⌘N target rule (settled); placeholder and abandon semantics exactly as ⌘N. The card window's attachments-section **quiet add affordance** (05) is the same class: a pointer twin of File ▸ Add Attachment…, no separate behavior.
 - **Attachment rows** drag out their file URL (05). **Welcome rows**: single click selects, double click opens (03).