UseClipboard

Copy-to-clipboard behavior: the clipboard write, a transient isCopied flag with its own reset timer, and an optional polite screen-reader announcement. Extracted so every copy affordance is a thin control over one implementation instead of re-deriving the timer and announcement. Rapid re-copies restart the reset timer so the confirmation always lasts the full duration, and the timer is cleaned up on unmount. CodeBlock and Timestamp build their built-in copy buttons on it; reach for it directly when building a copy affordance that is not a plain icon button (a menu item, a labeled text button, a copy-on-click value chip).