Disable sender tooltip and copy button in deleted messages

Editor assessment

The subject states a complete, self-evident rule: the sender tooltip and copy button are disabled for deleted messages, and any reader understands both the defect, interacting with content that no longer exists, and the remedy without the diff. Fix is the right type, the capitalized start is permitted, and the trailing pull-request number is the conventional squash-merge marker. The double space before the number is a trivial blemish. No body is needed for a contained UI guard; no footers, none needed. Hygiene is otherwise good. A clean, publishable message.