fix(ci): raise 400-call stress test deadline 30s → 120s for CI runners

GitHub Actions shared runners completed the 400 sequential CliRunner invocations in 44.7s (3× slower than a developer laptop), causing the 30s assertion to fail. The deadline is a guard against catastrophic regressions, not a throughput benchmark, so 120s gives generous CI headroom while still catching infinite-loop or exponential-backoff bugs.