feat(phase-13): implement recent files tracking system

Add recent files store for tracking recently opened/saved projects.

Features:
- Recent files store with persistence
- Track up to 10 recent files (configurable)
- Store file metadata:
  * Unique ID
  * File name
  * File path
  * Timestamp
  * Optional thumbnail
- Automatic duplicate removal (by path)
- Most recent files appear first
- Functions for managing recent files:
  * addRecentFile() - Add to recent list
  * removeRecentFile() - Remove specific file
  * clearRecentFiles() - Clear all recent
  * updateThumbnail() - Update file thumbnail
- localStorage persistence

Changes:
- Created store/recent-files-store.ts with RecentFile interface
- Exported from store/index.ts
- Ready for UI integration in File menu

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

store/index.ts

@@ -12,3 +12,4 @@ export * from './ui-store';
 export * from './toast-store';
 export * from './context-menu-store';
 export * from './guides-store';
+export * from './recent-files-store';

store/recent-files-store.ts

@@ -0,0 +1,78 @@
+import { create } from 'zustand';
+import { persist } from 'zustand/middleware';
+
+export interface RecentFile {
+  id: string;
+  name: string;
+  path: string;
+  timestamp: number;
+  thumbnail?: string;
+}
+
+interface RecentFilesStore {
+  /** List of recent files */
+  recentFiles: RecentFile[];
+  /** Maximum number of recent files to keep */
+  maxRecent: number;
+
+  /** Add file to recent list */
+  addRecentFile: (name: string, path: string, thumbnail?: string) => void;
+  /** Remove file from recent list */
+  removeRecentFile: (id: string) => void;
+  /** Clear all recent files */
+  clearRecentFiles: () => void;
+  /** Update file thumbnail */
+  updateThumbnail: (id: string, thumbnail: string) => void;
+}
+
+export const useRecentFilesStore = create<RecentFilesStore>()(
+  persist(
+    (set, get) => ({
+      recentFiles: [],
+      maxRecent: 10,
+
+      addRecentFile: (name, path, thumbnail) => {
+        const id = `${path}-${Date.now()}`;
+        const newFile: RecentFile = {
+          id,
+          name,
+          path,
+          timestamp: Date.now(),
+          thumbnail,
+        };
+
+        set((state) => {
+          // Remove duplicate if exists (same path)
+          const filtered = state.recentFiles.filter((f) => f.path !== path);
+          // Add new file at the beginning
+          const updated = [newFile, ...filtered];
+          // Keep only maxRecent files
+          return {
+            recentFiles: updated.slice(0, state.maxRecent),
+          };
+        });
+      },
+
+      removeRecentFile: (id) => {
+        set((state) => ({
+          recentFiles: state.recentFiles.filter((f) => f.id !== id),
+        }));
+      },
+
+      clearRecentFiles: () => {
+        set({ recentFiles: [] });
+      },
+
+      updateThumbnail: (id, thumbnail) => {
+        set((state) => ({
+          recentFiles: state.recentFiles.map((f) =>
+            f.id === id ? { ...f, thumbnail } : f
+          ),
+        }));
+      },
+    }),
+    {
+      name: 'recent-files-storage',
+    }
+  )
+);