feat: add manual onboarding flow alias

docs/cli/onboard.md

@@ -16,6 +16,10 @@ Related:
 ```bash
 clawdbot onboard
 clawdbot onboard --flow quickstart
+clawdbot onboard --flow manual
 clawdbot onboard --mode remote --remote-url ws://gateway-host:18789
 ```
 
+Flow notes:
+- `quickstart`: minimal prompts, auto-generates a gateway token.
+- `manual`: full prompts for port/bind/auth (alias of `advanced`).