Settle within-board lane paste as the supported lane duplicate

04's drag rule called a within-board lane duplicate unsupported while the
clipboard rules quietly permitted it via same-board lane paste. Settled in
favor of the clipboard: the duplicate is supported there (fresh GUIDs,
tombstones stripped, no menu-validation special case) and merely not
available by drag — ⌥ stays ignored on lane drags so the gesture remains a
clean reorder.

Claude-Session: https://claude.ai/code/session_01HJ7PhFNmQ19bvy9RMD6GSb

DESIGN/04-interactions.md

@@ -15,7 +15,7 @@ Selection, drag & drop, keyboard, clipboard, search. This is where the old app s
 - Cards reorder within a lane and move between lanes (folder move). Lanes reorder; a full-size replica travels under the cursor.
 - **Multi-drag**: dragging any member of a multi-selection drags the whole selection; N contiguous shadows; drop inserts contiguously in preserved relative order — defined, for any multi-selection, as lane `order` first, then card `order` (a cross-lane selection flattens left-to-right, top-to-bottom).
 - **Locality picks the default — the Finder volume model** (settled): within a board a drag is a **move** (rearranging); between boards it is a **copy** (transferring — the system copy badge shows over the foreign board). **⌥ always forces copy** and **⌘ always forces move**, Finder's exact modifier grammar; each is a no-op where its behavior is already the default. The badge tracks the effective operation live as the cursor crosses a board boundary.
-- **Within-board ⌥-drag copies**: originals stay, cursor shows the copy badge, fresh-GUID duplicates land at the drop. Lane drags never copy *within their board* — a lane duplicate inside its own board stays unsupported; ⌥ is simply ignored there (the drag stays a move and the badge never shows copy).
+- **Within-board ⌥-drag copies**: originals stay, cursor shows the copy badge, fresh-GUID duplicates land at the drop. Lane drags never copy *within their board* — a within-board lane duplicate is **not available by drag** (⌥ is simply ignored there: the drag stays a clean reorder and the badge never shows copy); the duplicate itself is supported, via the clipboard (Lane paste below) — the usual shape: the keyboard path is the canonical one, drag the enhancement (10-accessibility.md).
 - **Cross-board copy** (the default): cards and lanes (including multi-selections) drag between open boards; fresh-GUID duplicates land at the drop, originals stay, `created` is kept (a copy is a fork — 01-storage-format.md). Lanes copy cards and all — transferring workflow structure between boards is safe by default. A lane copy **strips tombstoned cards**: the copy transfers content, and trash isn't content (09-templates.md's instantiation precedent — a board isn't born with trash); the tombstoned originals stay recoverable in the source board. A ⌘-drag *move* carries them whole — the folder moves as-is, and they land in the destination's trash.
 - **Cross-board move** (⌘-drag): a real filesystem move, works across volumes — identity travels. A moved folder whose UUID already exists in the destination board arrives as a fresh-UUID copy (01-storage-format.md's import-boundary rule); in a compound move (lane with cards, multi-selection) only the colliding folders are reminted — the rest is a true move (01's per-folder degradation).
 - **Files from Finder**: dropped on a card → copied into its `attachments/` (any type, multi-file; card highlights while hovered). Dropped on lane empty space → creates a card with the file attached, titled with the filename without its extension (multi-file drop: one card per file).
@@ -26,7 +26,7 @@ Selection, drag & drop, keyboard, clipboard, search. This is where the old app s
 - ⌘X/⌘C/⌘V on cards **and lanes** (resettled — lanes joined the clipboard so cross-board structure transfer has a keyboard path under the every-function contract; the cards-XOR-lanes selection rule means the clipboard holds cards or lanes, never both). Hybrid clipboard: pasteboard carries a JSON manifest + plain text; full folder snapshots staged in Application Support so paste reproduces the item byte-for-byte — cards, attachments and all — across boards. Each manifest entry embeds the full `index.md` as a staging-less fallback (a lane entry embeds its cards' too, attachment-less). **Staging lifecycle** (settled): snapshots are staged **eagerly at ⌘C/⌘X time** — copy captures the source as it is at the gesture, immune to later deletion or unmount — and the store holds at most the *current* copy: a new Lanework copy replaces the previous snapshot, and a sweep at launch and on each copy purges entries the pasteboard no longer references (another app taking the pasteboard orphans the snapshot; the next sweep collects it). The snapshot survives relaunch exactly as long as the pasteboard still points at it — a copy made before quitting pastes whole after restart. **A degraded paste is loud, never silent** (the banner vocabulary — 02-architecture.md): if the staged snapshot is missing or unreadable at paste time, paste falls back to the embedded `index.md` — content intact, attachments absent — and a one-shot banner names exactly what was lost ("Pasted 'Fix login' without its 3 attachments"); the user never discovers an empty `attachments/` later.
 - **Cut is Finder-style deferred**: cut items dim in place until paste moves them; voided if another app takes the pasteboard or the source board closes; second paste materializes copies. **Deletion voids per item**: a cut item that is tombstoned or vanishes externally before paste drops out of the pending cut — 02-architecture.md's UUID-set rule; transient state never resurrects what's gone — so paste moves only the survivors, and a cut voided down to nothing is simply void (paste disabled, no error).
 - Paste lands after the anchor card (or appends to a selected lane). Copies keep `created` (a duplicate is a fork) and take fresh GUID/`order`/`modified`.
-- **Lane paste** lands after the anchor lane — the selected lane, or the selected card's lane; nothing selected = the board's right end. Semantics mirror the drag pair above exactly: a pasted *copy* takes fresh GUIDs throughout and **strips tombstoned cards**; a cut-paste is the ⌘-drag move — the folder moves whole, tombstoned cards landing in the destination's trash.
+- **Lane paste** lands after the anchor lane — the selected lane, or the selected card's lane; nothing selected = the board's right end. Semantics mirror the drag pair above exactly: a pasted *copy* takes fresh GUIDs throughout and **strips tombstoned cards**; a cut-paste is the ⌘-drag move — the folder moves whole, tombstoned cards landing in the destination's trash. **Pasting into the source board is supported and is the within-board lane duplicate** (settled): fresh GUIDs and tombstone-stripping apply as anywhere else, no menu-validation special case — the drag path deliberately lacks this operation (⌥ ignored on lane drags, above), the clipboard is its one home.
 
 ## Keyboard