[Yuqing (mydmdm)]

Summary

• Replace the native browser context menu on Files explorer file/folder rows with Copy name, Copy relative path, and Copy full path.
• Resolve relative paths from the currently opened root using displayed ancestry, preserving symlink names and the source device's separators; copy full device paths without URL encoding or shell quoting.
• Reuse Common DropdownMenu and the existing clipboard helper/fallback. An independent actions button becomes visible on hover or keyboard focus; Shift+F10, the Context Menu key, standard menu navigation, Escape and outside dismissal work without nesting interactive controls.
• Keep the path input's native editing menu and existing disclosure, Add and copy-only drag behavior. Surface clipboard failures and clear them on successful retry.
• Add English/Chinese labels and document the behavior in the device-files architecture reference.

Validation

• pnpm typecheck
• pnpm format
• pnpm lint:fix
• 48 focused tests across FilesPanel, Common DropdownMenu and clipboard suites.
• pnpm check:i18n and node scripts/check-headers.mjs.

Coverage includes file/folder metadata-only copying, nested POSIX/Windows/UNC paths, symlink hierarchy and root aliases, literal Unicode/backslash/space/shell-like names, context-menu event cancellation on rows/menu items but not path inputs, keyboard navigation/dismissal, clipboard failure/retry, and existing lazy expansion/Add/drag/root-switch behavior. Native browser menus are suppressed through contextmenu.preventDefault(); platform-specific native menu contents were not inspected in Windows/macOS desktop runs.

This is the user-approved follow-up to merged #355. No new API, dependency, file-content read or filesystem mutation is introduced.

References #349.