fix(cli): keep route-first json stdout clean

docs/cli/models.md

@@ -111,6 +111,10 @@ Options:
 - `--probe-max-tokens <n>`
 - `--agent <id>` (configured agent id; overrides `OPENCLAW_AGENT_DIR`/`PI_CODING_AGENT_DIR`)
 
+`--json` keeps stdout reserved for the JSON payload. Auth-profile, provider,
+and startup diagnostics are routed to stderr so scripts can pipe stdout directly
+into tools such as `jq`.
+
 Probe status buckets:
 
 - `ok`