Relocate loose card files into attachments

01's Lanework-owns-the-board carve-out: a regular file beside a card's
index.md belongs in attachments/, and the app moves it there. The
loader detects read-only — a new LoadResult.looseCardFiles channel,
separate from the stray-tolerance warnings because it says the opposite
thing — skipping directories, symlinks, hidden entries, and the
reserved names compared case-insensitively (on APFS, Index.md IS the
index). The relocation rides one performWrite bracket at the tail of
every successful reload, which makes lock deferral free: the reload
that lifts a read-only lock is the reload that relocates. A
lane/card/filename memo keeps a failing relocation from hot-looping —
one one-shot, then silence until disk changes. The notice rides the
loss-row class, phrasing folded by BannerCenter (one file, one card's
files, a multi-card sweep), naming original filenames per the
importAttachment rule. Paste normalizes at the import boundary: staged
snapshots' loose files land in the pasted card's attachments silently,
every arrival path declaring its side via an explicit
normalizingLooseFiles parameter — drag paths decline and fall back to
the destination's own carve-out. checkIsCardFolder closes the hole
where a lane's notes.txt would have been relocated: card depth is
exact, UUID under UUID.

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

README.md

@@ -9,7 +9,7 @@ The defining consequence: anything that can read and write files is a first-clas
 Lanework is in early development. This list tracks what has actually shipped and grows milestone by milestone; the full design lives in [DESIGN/](DESIGN/).
 
 - **Storage contract, read side** — frontmatter engine with a byte-perfect round-trip guarantee (unknown keys, comments, and formatting survive every rewrite; duplicate keys read last-wins; wrong-type scalars coerce read-side), gapped fractional ordering (Ranks), and a fail-fast board loader with UUID-gated level detection, warning-collecting skips, and tombstone-aware snapshots — pinned by a golden fixture suite of 18 on-disk boards.
-- **Storage contract, write side** — BoardWriter turns every mutation into an atomic temp-file+rename over exactly the files it touches: creates mint lowercase-UUIDv4 identities and `.kanban` packages; moves keep the UUID (with per-folder collision repair at the cross-board import boundary); copies mint fresh identities at every level; deletes are in-place tombstones with position-perfect restore and physical purge; attachment imports never overwrite and never refuse (Finder-style renames). Every app write stamps `modified`, clears `modified-by`, and preserves everything it didn't change byte-for-byte; readable-but-uneditable frontmatter shapes refuse loudly instead of corrupting.
+- **Storage contract, write side** — BoardWriter turns every mutation into an atomic temp-file+rename over exactly the files it touches: creates mint lowercase-UUIDv4 identities and `.kanban` packages; moves keep the UUID (with per-folder collision repair at the cross-board import boundary); copies mint fresh identities at every level; deletes are in-place tombstones with position-perfect restore and physical purge; attachment imports never overwrite and never refuse (Finder-style renames). Every app write stamps `modified`, clears `modified-by`, and preserves everything it didn't change byte-for-byte; readable-but-uneditable frontmatter shapes refuse loudly instead of corrupting. Strays are preserved verbatim everywhere with exactly one carve-out: a loose *file* dropped beside a card's `index.md` belongs in that card's `attachments/`, so the app moves it there — Finder-renamed on collision, byte-faithfully, without touching `index.md` — and says so in a dismissable warning row naming the card and the files. Detection stays read-only in the loader; the move is an ordinary bracketed write that waits out the read-only lock and never retries a failure in a loop. Stray *folders*, symlinks, and everything at board or lane level keep the verbatim posture untouched, and a paste normalizes at the import boundary so a pasted card lands already tidy.
 - **Live store** — every open board is one shared, watched, in-memory snapshot: an FSEvents folder watcher (debounced, `.git`-filtered, origin-reconciling) drives whole-tree reloads with a generation guard and single-flight coalescing; write brackets suppress self-echo; a file-identity-keyed store registry refcounts stores and watchers across windows and absorbs root renames via bookmark re-resolution (a vanished root locks the board and watches for its return); plus the board registry (recents, bookmarks, cached counts), the banner center's single precedence order, the dirty-buffer guard, and transient UI state.
 - **Window architecture** — the three window types and their lifecycle: a welcome window (below), one board window per root (per-board frame memory, repositioned onto a live screen), and at-most-one card window per card (last-used size, cascaded; follows its card across lanes; dismisses on delete, tombstone, or cross-board move). Closing a board window or quitting runs one strict close flush — card sessions end, pending work drains, the registry is stamped — before the store tears down; launch restores the boards whose open-now flags survived quit (or crash), a preference gating only whether the flags are consulted.
 - **The board** — every lane always on screen, the window's width dividing across the lanes' width units with no horizontal scroll: cards flow into as many interior masonry columns as a lane is wide, a right-edge drag resizes between whole units by growing the *window* (snapping at the gap with release hysteresis, hard-stopping at the screen with rubber-band feedback), and ⌥⌘→/⌥⌘← re-divide the existing width instead. Lane chrome is a per-lane SF Symbol (unknown names fall back leniently), title or untitled placeholder, a card-count badge that counts exactly what's rendered, and a new-card button — the whole title bar doubling as the drag surface, a plain click selecting the lane and movement carrying it away.