Docs tests: add CLI startup benchmark usage

docs/reference/test.md

@@ -43,6 +43,26 @@ Last run (2025-12-31, 20 runs):
 - minimax median 1279ms (min 1114, max 2431)
 - opus median 2454ms (min 1224, max 3170)
 
+## CLI startup bench
+
+Script: [`scripts/bench-cli-startup.ts`](https://github.com/openclaw/openclaw/blob/main/scripts/bench-cli-startup.ts)
+
+Usage:
+
+- `pnpm tsx scripts/bench-cli-startup.ts`
+- `pnpm tsx scripts/bench-cli-startup.ts --runs 12`
+- `pnpm tsx scripts/bench-cli-startup.ts --entry dist/entry.js --timeout-ms 45000`
+
+This benchmarks these commands:
+
+- `--version`
+- `--help`
+- `health --json`
+- `status --json`
+- `status`
+
+Output includes avg, p50, p95, min/max, and exit-code/signal distribution for each command.
+
 ## Onboarding E2E (Docker)
 
 Docker is optional; this is only needed for containerized onboarding smoke tests.