[Hooks] Implement Native OS Integration Hooks (File/Folder Dialogs & Clipboard)

Problem Statement

Applications built with rusty targeting native desktop environments require reactive hooks for invoking native OS dialogs and interacting with the system clipboard (use_file_dialog, use_folder_dialog, use_save_dialog, use_clipboard).

Missing Functionality

• use_file_dialog: Hook to prompt native file open picker with file filters.
• use_folder_dialog: Hook to prompt native directory/folder picker.
• use_save_dialog: Hook to prompt native save file picker with default names and extensions.
• use_clipboard: Asynchronous read/write hook for system clipboard text and data.

Proposed Architecture & Design

1. Implement hooks in rusty/src/hooks/os.rs.
2. For native desktop targets, delegate to rfd (Rust Native File Dialogs) and arboard (clipboard).
3. For WebAssembly / browser targets, fallback to HTML5 Input/File API and navigator.clipboard.

Acceptance Criteria

• use_file_dialog, use_folder_dialog, use_save_dialog trigger native file selection pickers on desktop targets.
• use_clipboard provides reactive copy and paste operations across platforms.
• Fallback behavior handles web browser environments gracefully.

Start by reading rusty/src/hooks/os.rs and comparing the native and WebAssembly targets described in the issue. Check how rfd, arboard, HTML5 Input/File APIs, and navigator.clipboard would map to the four proposed hooks. Done means the three dialogs work on desktop, clipboard copy and paste are reactive across platforms, and browser fallback behavior is graceful.