refactor(store): Extract utility functions into store/utils/

Move pure utility functions from app-store.ts and type files into
dedicated utils modules for better separation of concerns:

- theme-utils.ts: Theme and font storage utilities
- shortcut-utils.ts: Keyboard shortcut parsing/formatting
- usage-utils.ts: Usage limit checking

All utilities are re-exported from store/utils/index.ts and
app-store.ts maintains backward compatibility for existing imports.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/ui/src/store/utils/shortcut-utils.ts

@@ -0,0 +1,117 @@
+import type { ShortcutKey, KeyboardShortcuts } from '../types/ui-types';
+
+// Helper to parse shortcut string to ShortcutKey object
+export function parseShortcut(shortcut: string | undefined | null): ShortcutKey {
+  if (!shortcut) return { key: '' };
+  const parts = shortcut.split('+').map((p) => p.trim());
+  const result: ShortcutKey = { key: parts[parts.length - 1] };
+
+  // Normalize common OS-specific modifiers (Cmd/Ctrl/Win/Super symbols) into cmdCtrl
+  for (let i = 0; i < parts.length - 1; i++) {
+    const modifier = parts[i].toLowerCase();
+    if (modifier === 'shift') result.shift = true;
+    else if (
+      modifier === 'cmd' ||
+      modifier === 'ctrl' ||
+      modifier === 'win' ||
+      modifier === 'super' ||
+      modifier === '⌘' ||
+      modifier === '^' ||
+      modifier === '⊞' ||
+      modifier === '◆'
+    )
+      result.cmdCtrl = true;
+    else if (modifier === 'alt' || modifier === 'opt' || modifier === 'option' || modifier === '⌥')
+      result.alt = true;
+  }
+
+  return result;
+}
+
+// Helper to format ShortcutKey to display string
+export function formatShortcut(shortcut: string | undefined | null, forDisplay = false): string {
+  if (!shortcut) return '';
+  const parsed = parseShortcut(shortcut);
+  const parts: string[] = [];
+
+  // Prefer User-Agent Client Hints when available; fall back to legacy
+  const platform: 'darwin' | 'win32' | 'linux' = (() => {
+    if (typeof navigator === 'undefined') return 'linux';
+
+    const uaPlatform = (
+      navigator as Navigator & { userAgentData?: { platform?: string } }
+    ).userAgentData?.platform?.toLowerCase?.();
+    const legacyPlatform = navigator.platform?.toLowerCase?.();
+    const platformString = uaPlatform || legacyPlatform || '';
+
+    if (platformString.includes('mac')) return 'darwin';
+    if (platformString.includes('win')) return 'win32';
+    return 'linux';
+  })();
+
+  // Primary modifier - OS-specific
+  if (parsed.cmdCtrl) {
+    if (forDisplay) {
+      parts.push(platform === 'darwin' ? '⌘' : platform === 'win32' ? '⊞' : '◆');
+    } else {
+      parts.push(platform === 'darwin' ? 'Cmd' : platform === 'win32' ? 'Win' : 'Super');
+    }
+  }
+
+  // Alt/Option
+  if (parsed.alt) {
+    parts.push(
+      forDisplay ? (platform === 'darwin' ? '⌥' : 'Alt') : platform === 'darwin' ? 'Opt' : 'Alt'
+    );
+  }
+
+  // Shift
+  if (parsed.shift) {
+    parts.push(forDisplay ? '⇧' : 'Shift');
+  }
+
+  parts.push(parsed.key.toUpperCase());
+
+  // Add spacing when displaying symbols
+  return parts.join(forDisplay ? ' ' : '+');
+}
+
+// Default keyboard shortcuts
+export const DEFAULT_KEYBOARD_SHORTCUTS: KeyboardShortcuts = {
+  // Navigation
+  board: 'K',
+  graph: 'H',
+  agent: 'A',
+  spec: 'D',
+  context: 'C',
+  memory: 'Y',
+  settings: 'S',
+  projectSettings: 'Shift+S',
+  terminal: 'T',
+  ideation: 'I',
+  notifications: 'X',
+  githubIssues: 'G',
+  githubPrs: 'R',
+
+  // UI
+  toggleSidebar: '`',
+
+  // Actions
+  // Note: Some shortcuts share the same key (e.g., "N" for addFeature, newSession)
+  // This is intentional as they are context-specific and only active in their respective views
+  addFeature: 'N', // Only active in board view
+  addContextFile: 'N', // Only active in context view
+  startNext: 'G', // Only active in board view
+  newSession: 'N', // Only active in agent view
+  openProject: 'O', // Global shortcut
+  projectPicker: 'P', // Global shortcut
+  cyclePrevProject: 'Q', // Global shortcut
+  cycleNextProject: 'E', // Global shortcut
+
+  // Terminal shortcuts (only active in terminal view)
+  // Using Alt modifier to avoid conflicts with both terminal signals AND browser shortcuts
+  splitTerminalRight: 'Alt+D',
+  splitTerminalDown: 'Alt+S',
+  closeTerminal: 'Alt+W',
+  newTerminalTab: 'Alt+T',
+};