Merge branch 'fix/cli-45-credential-envvar'

# Conflicts:
#	archreview/2026-07-12/remediation/00-tracking.md

clients/java/README.md

@@ -172,8 +172,13 @@ session.write(serverHandle, itemHandle, value, userId);
 native failure is surfaced, not papered over.
 
 The CLI exposes `advise-supervisory`, `write-secured`, and `authenticate-user`
-(credential via `--password` or `--password-env`, never echoed), and `write` /
-`write2` take `--user-id`.
+(credential via `--password` or the variable named by `--password-env`, default
+`MXGATEWAY_VERIFY_PASSWORD`, never echoed), and `write` / `write2` take
+`--user-id`. The credential is required: a missing or empty resolved value is a
+picocli usage error naming the option and the variable, so the CLI fails before
+connecting instead of authenticating with an empty password.
+`MXGATEWAY_VERIFY_PASSWORD` is the canonical variable across all five client
+CLIs — see [Cross-Language Smoke Matrix](../../docs/CrossLanguageSmokeMatrix.md).
 
 ### Array writes replace the whole array