Menu component conventions

• Framework: React with TypeScript.
• Styling: existing menu-* utility classes; do not add a styling dependency.
• Public components accept className and forward a DOM ref.
• Components must support keyboard-only and screen-reader users.
• Focus returns to the trigger when a menu closes.
• Escape closes the menu; arrow keys move between enabled items.

The new dropdown should expose a trigger label and an array of actions. Disabled actions remain visible but cannot receive focus or execute.