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media story (03, 01, 10, 11; the same-day carousel settlements superseded on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/08-agent-integration.md

@@ -18,7 +18,7 @@ The app silently maintains a `CLAUDE.md` in every board — a condensed, agent-f
 - Creating cards (mkdir UUID, write `index.md`, ordering rules) — plain UTF-8, no BOM, preserving each file's existing line endings (01-storage-format.md's encoding contract).
 - Moving between lanes (folder move), reordering (gapped ranks, only touch the moved item).
 - Tombstone deletes, colors/icons.
-- New in the rewrite: **attachments** (the `attachments/` convention, importing files).
+- New in the rewrite: **attachments** (the `attachments/` convention, importing files) — including the rule that **card files belong in `attachments/`**: a loose file written beside `index.md` will be relocated there by the app with a notice (01-storage-format.md's loose-file carve-out), so agents should put it there in the first place.
 - New in the rewrite: **`modified-by` self-stamping** — stamp files you write; re-stamp every write *and every move* (the app clears it on its own writes; a bare folder move leaves the card unstamped); self-commit instead when you need exact authorship.
 - New in the rewrite: a pointer to the optional **`CLAUDE.user.md`** (see below), instructing agents to read it when present.