CLI: name agent and terminal sessions at creation (--title)

Summary

• We want to set a terminal/agent session title at creation time from the CLI
• v1.29 shipped session naming on desktop and phone, but superset terminals create and superset agents create expose no title flag
• Workspace naming is already covered (workspaces create --name / workspaces update) — this is only about the session title inside a workspace

Today superset workspaces create --name names the lane, and the desktop/phone UI can name a terminal session — but a session created headlessly (terminals create, agents create) gets an auto-derived title, and there is no CLI/API way to set or change it. An automation fleet dispatching one agent per issue would like the session titled to match its task (e.g. reviewer seats vs worker lanes in one workspace).

Proposal A --title option on superset terminals create and superset agents create, e.g. --title "seat: PR 994", plus a rename command (or API) for existing sessions so a title can be set after adoption or handoff.

Environment Superset 1.29.0 (CLI and host service), macOS arm64