feat(rust-client): operator credentials on acknowledge-alarm

Claude-Session: https://claude.ai/code/session_016J6isfcgqy4SB2RK3ZvFvT

clients/rust/RustClientDesign.md

@@ -174,6 +174,8 @@ alarm monitor — no worker session is opened — so any number of clients may
 attach. Dropping the stream cancels the gRPC call cooperatively.
 `acknowledge_alarm` is idempotent at the MxAccess layer; the returned
 `AcknowledgeAlarmReply` carries the native MxStatus from the worker.
+`operator_user` is required; `operator_password` may be empty and is scrubbed from any
+returned error via `Error::redact_secrets`.
 
 ## Galaxy Repository
 
@@ -346,7 +348,7 @@ mxgw write-secured-bulk ...
 mxgw write-secured2-bulk ...
 mxgw stream-events --session-id <id> --json
 mxgw stream-alarms [--filter-prefix <prefix>] [--max-events <n>]
-mxgw acknowledge-alarm --reference <full-ref> [--comment <txt>] [--operator <user>]
+mxgw acknowledge-alarm --reference <full-ref> [--comment <txt>] --operator <user> [--operator-domain <domain>] [--operator-password-env <VAR>=MXGATEWAY_OPERATOR_PASSWORD] [--operator-password <pw>]
 mxgw bench-read-bulk [--duration-seconds <n>] [--warmup-seconds <n>] [--bulk-size <n>]
 mxgw smoke --endpoint http://localhost:5000 --api-key-env MXGATEWAY_API_KEY --item TestChildObject.TestInt
 mxgw batch