Implement the hybrid clipboard with deferred cut

⌘X/⌘C/⌘V for cards and lanes per 04-interactions.md § Clipboard:

- ClipboardStore stages full folder snapshots eagerly at the gesture into
  Application Support (at most the current copy; sweep at launch and on
  each copy purges what the pasteboard no longer references; a copy made
  before quitting pastes whole after restart) and writes the pasteboard a
  JSON manifest — every entry embedding its index.md, lane entries their
  cards' too — plus plain-text titles.
- Cut is Finder-style deferred: items dim in place off pendingCut, void on
  pasteboard takeover (changeCount, no timers), source-board close, or
  per-item external tombstoning; the first armed paste moves the surviving
  originals whole (tombstoned interior cards land in the destination's
  trash), a second paste materializes copies from staging.
- Paste anchors by the shared flatten-order rule (NewCardTarget's anchor,
  extracted); a tombstoned selection never anchors; lane paste reaches the
  right end and stays enabled on a zero-lane board; paste into the source
  board is the within-board lane duplicate; copies keep created, take
  fresh GUIDs, and strip tombstoned cards; trash-sourced copies strip
  deleted: at materialization; ⌘X is disabled on the trash side.
- A degraded paste is loud, never silent: staging gone → the embedded
  index.md fallback lands content-intact, attachments absent, and a
  BannerCenter-phrased row names what was lost.
- The standard Edit items validate through conditionally-attached
  onCommand handlers, so AppKit's enablement mirrors the availability
  predicates; text fields keep their own clipboard while focused.

879 unit tests (68 new).

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

README.md

@@ -20,6 +20,8 @@ Lanework is in early development. This list tracks what has actually shipped and
 
 - **The keyboard** — the board is fully operable without the mouse, and every board function has a menu item. Arrows walk to the nearest card in the direction — across a lane's interior masonry columns, across lanes, and into and out of the shown trash — with ⇧-arrows extending the range from the anchor and stopping dead at the liveness and card/lane-entry boundaries rather than silently reaching past them. ⌥-arrows jump: ⌥↑/⌥↓ to the lane's first/last card, ⌥←/⌥→ to the first/last lane (⌥→ reaching the trash when it's shown), and a second ⌥↑ on a lane's first card escalates into selecting the lane itself — the one keyboard entry to lane selection, from which ←/→ move between lanes, ↓ descends back into the cards, and an empty selection seeds at the first lane's first card so an arrow from nothing always means the same thing. The selection scrolls itself into view. The Board menu carries the rest: Open Card (⌘↩) — the one command that stays live mid-edit, committing the title and opening the window — Move Up/Move Down (⌥⌘↑/⌥⌘↓), which sort within a lane in logical order and gather a scattered selection into a block behind its first card on the first press, and Move Left/Move Right (⌘←/⌘→), which slide a selected lane one slot and never into the trash. Deleting picks the successor sibling Finder-style, so repeated ⌫ walks down a lane; an external deletion deliberately doesn't.
 
+- **The clipboard** — ⌘X/⌘C/⌘V move cards *and* lanes, within a board and across boards, so structure transfers without a mouse. It's a hybrid: the pasteboard carries a small manifest plus the titles as plain text, while the real content — whole folders, attachments and strays and all — is snapshotted into Application Support the instant you press ⌘C, so a copy captures the item as it was at that moment and survives the original being deleted, its volume unmounting, or the app quitting and relaunching. The store keeps exactly one snapshot: every copy and every launch sweeps whatever the pasteboard no longer points at. If a snapshot has gone missing by the time you paste, the manifest still carries each item's full `index.md`, so the paste lands with its content intact — and says so out loud, naming exactly what was left behind ("Pasted 'Fix login' without its 2 attachments") rather than leaving you to find an empty `attachments/` later. Cut is Finder-style deferred: the items dim in place and stay put until a paste moves them, voiding if another app takes the pasteboard or the source board closes (the paste then quietly becomes a copy), and voiding *per item* if one is deleted in the meantime — so a paste moves whatever survived, and a cut emptied down to nothing simply does nothing. Paste lands after the anchor card, at a selected lane's bottom, or at the last member of a multi-selection in flatten order — the same anchor ⌘N uses — and a lane payload lands after the anchor lane or at the board's right end, which is one of the two ways out of a board with no lanes at all. Copies keep `created` and take fresh identities throughout; a pasted lane strips tombstoned cards while a cut lane carries them whole; pasting a lane back into its own board is the within-board duplicate the drag deliberately doesn't offer. The trash is copy-out only — ⌘C on a trash row (card or lane entry) yields a live copy with the tombstone stripped, ⌘X is disabled there — and the read-only lock blocks cut without ever blocking copy, because copying out is a read.
+
 - **Styling** — one style editor serves every anchor: a background grid of the twelve palette wells behind a leading None well that *removes* the key, and a curated grid of five dozen kanban-relevant SF Symbols behind a leading level-default well that does the same. It is selection-aware (the selected cards or lanes; the board with nothing selected) and states the current value per dimension across the whole target set — agreement selects a well, disagreement reads "—", and a hand-written hex or uncurated symbol states itself verbatim outside the grids, replaced by any well you choose. A batch applies as one bracketed commit that skips every target already carrying the value, and the open editor tracks its targets live: one deleted out from under it leaves the set, and the last one closes the editor rather than quietly retargeting the board. Reached from Board ▸ Style… (⌥⌘S) or a card's or lane's context menu, where a compact row of app-wide recent colours recolours in one click and a lane's menu also carries its width stepper. Colour renders at all three levels — a card's `background` as a left-edge stripe, a lane's as a full-width band along its top edge, the board's as the window's content background — each painting nothing at all when the value doesn't resolve, bytes on disk untouched.
 
 - **The trash** — deletion is two-stage and Finder-shaped. File ▸ Delete (⌘⌫, or a plain ⌫) tombstones the selection in place — cards or lanes, one bracketed write for the whole batch — and View ▸ Show Trash reveals a trailing quasi-lane where tombstoned items live. It is a pure view: nothing moves on disk, so Put Back is byte-perfect and returns an item to its old position. The column takes exactly one width unit while shown, so showing it re-divides the window rather than resizing it. Its order is fully deterministic (newest deletion first, ties by folder name, an unreadable timestamp sorting oldest) and its ancestor walk is absolute — a tombstoned lane is one entry subsuming everything beneath it, its count naming the cards Put Back would return, so recovering a separately deleted card inside it is deliberately two steps. Drag a row out onto any lane to restore it there. Purging is Delete Immediately (⌥⌘⌫) and Empty Trash… (⇧⌘⌫), each confirmed where the loss is real and named by count; Empty Trash always covers the whole trash, never just what a filter is showing. Nothing edit-shaped — Open, Rename, Style… — applies to a tombstoned selection, and a selection never mixes trashed with live.