It would be convenient if --resume /resume could take a /rename session name as an argument

### Describe the feature or problem you'd like to solve

This would allow easily resuming without having to memorize a session id

### Proposed solution

If a user /rename s a session, allow using that as an alternate identifier. If matching is ambiguous, fallback to the current session picker experience.

### Example prompts or workflows

start a session
do stuff
/rename foo
exit

copilot /resume foo
you're ready to go

### Additional context

_No response_