Copy Link — a card context-menu row that puts the card folder on the pasteboard

Card 737a949f: "Add an option to card context menu to copy a link to
the card folder." Implements the design ruling verbatim.

- New context-menu row "Copy Link" (CardFaceView.boardMenu, board
  side only — trash cards are excluded, matching "sole selected live
  card"). Writes the clicked card's folder in one pasteboard item
  carrying two representations: the file:// URL under .fileURL and
  the plain absolute path under .string (FolderLinkPasteboard.swift).
  Enabled on a sole selected live card; disabled on a multi-selection
  and wherever edit-shaped actions already disable, per the ruling.
  Also exposed as a VoiceOver custom action alongside its siblings.
- Menu-bar twin: Board ▸ Copy Link (BoardCommands.swift,
  CopyLinkCommand), no default chord — the every-function-a-menu-item
  contract in DESIGN/11-command-nexus.md is still current, so this is
  the twin that contract calls for, homed the way Open Card/Rename/
  Style… already are.
- DESIGN/11-command-nexus.md: new Board-menu row and an updated Card
  context-menu row.
- Tests (KanbanTests/CopyLinkTests.swift): the target predicate's
  enablement (sole card / multi-selection / lane / trash / empty /
  inline-editing), the pasteboard write's exact bytes via a fake
  pasteboard (both representations, exact folder URL), and a
  disabled-target no-op.

Caught and fixed during self-review: an early version read the
context menu's widened-selection helper (targetIDs) inside the
Copy Link row's .disabled(...), which reads store.selection. Since
.contextMenu's content closure is evaluated on every ordinary body
pass (not only when the menu opens), that resubscribed every card
face on the board to every selection change — the exact O(board)
regression RENDER-INSTRUMENTATION.md's isSelected/selectedCount
split exists to prevent, caught by BoardRenderPerformanceTests and
MarqueeRenderCostTests. Fixed by reading the already-hoisted,
non-Observable `selectedCount` parameter instead, which answers the
same "how many ride along" question at zero extra subscription cost.

xcodegen generate, the Kanban scheme build, and the full KanbanTests
suite (2816 tests) are clean.

Claude-Session: https://claude.ai/code/session_014PtZdPwqZuqEDLc6wZMtEy

DESIGN/11-command-nexus.md

@@ -40,6 +40,7 @@ The single source of truth for **every command and action the app can perform**
 | Edit | Find | ⌘F | Board window: board search (04 ▸ Search); card window: find-in-text (05) |
 | Edit | Find Next / Find Previous | ⌘G / ⇧⌘G | Card window: the find bar's stepping — the rows enable only while the comments-thread find bar is up and step *that* bar; otherwise they disable and the chord falls through the responder chain to the focused text surface's own NSTextFinder stepping (pinned 2026-07-31 — routing by focus applied to find); disabled in the board window — board search is a live filter, not a cursor. **Use Selection for Find (⌘E) is deliberately absent**: the chord belongs to View ▸ Edit Body, which outranks the text view's binding; a user who wants it back remaps Edit Body system-natively |
 | Board | Open Card | ⌘↩ | Board window, sole selected live card; during an inline title edit (placeholder or rename), commits it and opens — the one board command enabled mid-edit (04 ▸ Grammar) |
+| Board | Copy Link | — (no default) | Board window, sole selected live card; writes the card folder's `file://` URL and plain absolute path to the pasteboard, one write, two representations; disabled on multi-selections and wherever edit-shaped actions disable (design ruling 2026-08-09) |
 | Board | Rename | — (cards: Return in place) | Board window, sole selected card/lane; a lane's only rename path (Return on a lane creates); exists for completeness and remapping |
 | Board | Style… (the style editor; selection-aware) | ⌥⌘S | Board window: selected cards or lane; nothing selected = the board |
 | Board | Move Up / Move Down | ⌥⌘↑ / ⌥⌘↓ | Card selection within one lane (within-lane sort, logical order; non-contiguous selections gather behind their first card on the first press); disabled when the selection spans lanes; inert on lanes and on trash cards |
@@ -98,7 +99,7 @@ Context menus are the per-item action inventory VoiceOver reads (10 ▸ The boar
 
 | Surface | Entries |
 |---|---|
-| Card | Open, Rename, Style…, quick-style recents row (03), Delete (the ⌥-alternate Delete Immediately row retired with the command, 2026-07-30) |
+| Card | Open, Copy Link (folder link to the pasteboard — twin of Board ▸ Copy Link, 2026-08-09), Rename, Style…, quick-style recents row (03), Delete (the ⌥-alternate Delete Immediately row retired with the command, 2026-07-30) |
 | Lane | One menu, invoked on the header or lane empty space (settled — a full lane still has its header): Rename, Style…, quick-style recents row (03), Width control (stepper — menu twins Increase/Decrease Lane Width), Delete |
 | Trash selection | Delete (permanent — 03's recoverability confirm), Reveal in Finder (inspection before a purge; twin of File ▸ Reveal in Finder, not edit-shaped, enabled on trash selections — 04 ▸ The trash) |
 | Attachment row | Open, Remove (system Trash) — twins of the focused section's grammar keys (Return / ⌫ — 05); Reveal in Finder — twin of File ▸ Reveal in Finder in its attachments-focused context |