Add a way to list currently running Copilot CLI sessions with their status

Feature request: Anthropic's Claude Code CLI has a ⁠claude agents --json⁠ command that lists every currently-running interactive session on the machine, each with an id, name, cwd, and status (idle/busy/waiting/blocked). This makes it possible to build an external dashboard/monitor across multiple parallel sessions (e.g. several terminal tabs or IDE panes each running their own session).
Copilot CLI has no equivalent today — ⁠--resume⁠/⁠--session-id⁠/⁠/session⁠ all operate on a specific known session for resuming, not on discovering other currently-active sessions and their live state. The closest thing is the undocumented ⁠~/.copilot/session-state//events.jsonl⁠ per-session event log, but it's internal, unversioned, and provides no "is this session still alive" signal (no PID recorded anywhere).
Ask: a ⁠copilot sessions --json⁠ (or similar) command/flag that lists currently-active sessions with at least an id, working directory, and a coarse status (busy/idle, and ideally "waiting for tool permission" as a third state) — enabling external tooling to build a multi-session status dashboard the same way it's possible for Claude Code today.

Start by examining the existing session controls (--resume, --session-id, and /session) and the undocumented ~/.copilot/session-state//events.jsonl logs described in the issue. Determine how active sessions and their live state can be identified, then define completion around a JSON listing that reports each active session's id, working directory, and coarse status.