[FEATURE] Exit resume command should use custom session name from /rename instead of UUID

Preflight Checklist

• [x] I have searched existing requests and this feature hasn't been requested yet
• [x] This is a single feature request (not multiple features)

Problem Statement

When I rename a session with /rename, I expect to be able to use that name to resume the session. But the exit display shows the UUID, not the custom name — so I have to remember or look up the UUID separately. The name I set is essentially invisible at the one moment I need it most: when I'm resuming.

Proposed Solution

The "resume this session with:" command shown at exit should display the custom session name set via /rename instead of the UUID.

Current: claude --continue "xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"
Expected: claude --continue "my-session-name"

The custom name is already stored in the session JSONL as a custom-title event, and claude --continue "my-session-name" already works if typed manually. The exit display just needs to read the custom-title event and prefer it over the UUID.

Alternative Solutions

The status bar already reads and displays the custom session name correctly — the same logic could be applied to the exit display. Current workaround: note the session name separately and type the --continue command manually.

Priority

Medium - Would be very helpful

Feature Category

CLI commands and flags

Use Case Example

I rename sessions to track what I was working on (e.g., /rename research-synthesis). When I exit and want to resume the next day, the exit display shows a UUID I don't recognize. I have to either remember the name or dig through session files to find it.

Additional Context

Related to #42291 (custom-title not read in all code paths — that issue covers /clear, this covers the exit display). The fix scope appears small: read the custom-title event from the session JSONL in the exit display generator and use it when present.