Implement the keyboard grammar and full command map

The board's fixed grammar keys and the menu-backed chords of
04-interactions.md § Keyboard, per the Command Nexus inventory:

- Spatial arrow navigation (NavigationMath.nearest over the marquee
  registry's frames — one geometry source), walking across interior
  masonry columns, lanes, and into the shown trash; ⇧-arrows extend via
  the same range function as ⇧-click and go inert at the liveness and
  kind boundaries; ⌥-jumps with the ⌥↑ lane-domain escalation and ↓
  descent; the empty selection seeds at the first lane's first card;
  selection scrolls into view.
- selectionHead — the navigation cursor beside the anchor, set by every
  click, moved by every arrow, dropped by the reload vanish rule.
- Board ▸ Open Card ⌘↩ (the one command enabled mid-edit: commits the
  placeholder or rename and opens), Move Up/Move Down ⌥⌘↑/⌥⌘↓
  (within-lane sort, gather-then-step, rank-permuting writes in one
  bracket), Move Left/Move Right ⌘←/⌘→ (sole lane, one slot, never the
  trash) — all validating and acting off one shared answer.
- Delete now selects the Finder-style successor sibling from the
  pre-write snapshot, so repeated ⌫ walks down a lane; external
  vanishing still only shrinks the selection.
- handleReturn rejects modified Returns; the trash column renders
  eagerly so every row stays registered for navigation and the marquee.

686 unit tests (27 new).

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

Kanban/KanbanApp.swift

@@ -166,16 +166,22 @@ struct KanbanApp: App {
             ShowTrashCommand()
         }
 
-        // The Board menu (11-command-nexus.md), in its inventoried order — Rename, then Style…,
-        // then the width pair, with Open Card and the Move items still owed. Its items act on the
+        // The Board menu (11-command-nexus.md), complete and in its inventoried row order — Open
+        // Card, Rename, Style…, the card moves, the lane moves, the width pair. Its items act on the
         // frontmost board window, which they reach through the focus system rather than through the
         // app model — see `BoardCommands.swift`, which also owns their validation.
         CommandMenu("Board") {
+            OpenCardCommand()
             BoardRenameCommand()
             BoardStyleCommand()
 
             Divider()
 
+            MoveCardCommands()
+            MoveLaneCommands()
+
+            Divider()
+
             LaneWidthCommands()
         }