[FEATURE] Archive sessions (re-open of #65615)

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

Re-opening #65615 (closed as stale, locked). Still needed.

Sessions are either in agent view or deleted. No middle state for "done for now, will resume later," so named threads I'll return to are buried among hundreds of one-offs in /resume.

Proposed Solution

/archive (and claude archive <id>): hide a session from agent view and the default /resume list; show it in an Archived view; unarchive restores it.

Alternative Solutions

Pinning (keeps processes alive), name prefixes + /resume search.

Priority

Medium - Would be very helpful

Feature Category

Interactive mode (TUI)

Use Case Example

3–4 active sessions, ~12 parked long-running threads, hundreds of throwaways.