Move the following Rust commands from Tauri backend to ACP+ protocol. All these operations will be triggered from the Tauri frontend to invoke goose server. The Tauri Rust backend will become a thin layer.

Commands to migrate:

• commands::system::get_home_dir
• commands::sessions::save_exported_session_file
• commands::system::path_exists
• commands::system::list_directory_entries
• commands::attachments::inspect_attachment_paths
• commands::system::list_files_for_mentions
• commands::attachments::read_image_attachment