Surface current session's name/ID in the /resume picker (or prompt)

Problem

When you forget which session you're currently in, there's no way to check from inside that session — /resume lists other resumable sessions but omits the active one (understandably, since you can't resume into yourself). But the current session's human-friendly name and ID are already tracked (e.g. in ~/.claude/sessions/<pid>.json, which has sessionId and a derived name field) — they're just not surfaced anywhere in the UI.

Suggestion

Show the current session's name/ID somewhere always visible from inside the session — e.g. in the /resume list (greyed out / marked "current"), in the status line, or via a simple /whoami-style command — so a user who has lost track of which session they're in doesn't have to go spelunking in ~/.claude/sessions/*.json to find out.

Context

Ran into this while working in a terminal session and wanting to confirm which named session I was in without exiting.