Done! I've successfully removed arrow key navigation while preserving hjkl shortcuts. Here's what changed: (#946)

## Changes Made:

1. **[frontend/src/keyboard/registry.ts](file:///private/var/folders/m1/9q_ct1913z10v6wbnv54j25r0000gn/T/vibe-kanban/worktrees/155e-remove-keyboard/frontend/src/keyboard/registry.ts)**
   - Removed arrow keys from navigation bindings, kept only hjkl
   - Fixed Enter key conflict by changing fullscreen toggle to ⌘/Ctrl+Enter

2. **[docs/configuration-customisation/keyboard-shortcuts.mdx](file:///private/var/folders/m1/9q_ct1913z10v6wbnv54j25r0000gn/T/vibe-kanban/worktrees/155e-remove-keyboard/docs/configuration-customisation/keyboard-shortcuts.mdx)**
   - Updated Board Navigation section to show hjkl only
   - Added fullscreen toggle documentation

All type checks pass ✓

frontend/src/keyboard/registry.ts

@@ -91,28 +91,28 @@ export const keyBindings: KeyBinding[] = [
   },
   {
     action: Action.NAV_UP,
-    keys: ['up', 'k'],
+    keys: 'k',
     scopes: [Scope.KANBAN],
     description: 'Move up within column',
     group: 'Navigation',
   },
   {
     action: Action.NAV_DOWN,
-    keys: ['down', 'j'],
+    keys: 'j',
     scopes: [Scope.KANBAN],
     description: 'Move down within column',
     group: 'Navigation',
   },
   {
     action: Action.NAV_LEFT,
-    keys: ['left', 'h'],
+    keys: 'h',
     scopes: [Scope.KANBAN],
     description: 'Move to previous column',
     group: 'Navigation',
   },
   {
     action: Action.NAV_RIGHT,
-    keys: ['right', 'l'],
+    keys: 'l',
     scopes: [Scope.KANBAN],
     description: 'Move to next column',
     group: 'Navigation',
@@ -137,7 +137,7 @@ export const keyBindings: KeyBinding[] = [
   // Task panel actions
   {
     action: Action.TOGGLE_FULLSCREEN,
-    keys: 'enter',
+    keys: ['meta+enter', 'ctrl+enter'],
     scopes: [Scope.KANBAN],
     description: 'Toggle fullscreen view',
     group: 'Task Details',