Copilot CLI adds isolated parallel worktrees

GitHub Copilot CLI now exposes multiple concurrent sessions and 1 experimental /worktree command that starts a separate conversation inside an isolated Git worktree. GitHub’s weekly release also adds Git-independent rewind and live tool-call durations. Teams testing parallel coding agents should file this as harness progress, not proof of throughput: isolation can protect the main workspace, but six-agent trials still need explicit concurrency, cost, and integration budgets.