Feature request: ability to delete a session

There's currently no way to delete a single session transcript. claude project purge <path> deletes all state for a project (transcripts, tasks, file history, config entry), which is too coarse when you just want to clean up one or two stray/junk sessions.

Requesting either:

• a claude session delete <id> command, or
• a delete keybinding inside the /resume / -r picker (alongside the existing rename-with-Ctrl+R)

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(Originally filed together with a related bug report about orphan sessions; that part was split out into a separate issue for clearer tracking, see comment below.)