bxctl: escape frame errors; say the outcome is unknown after a timeout

From the independent review of task 23. serde quotes a bad frame's text after
decoding, so a compromised peer could put escape sequences in it. A timed-out
admin request now says whether brokerd acted is unknown, since it may have.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

crates/bxctl/tests/escape_details.rs

@@ -55,3 +55,21 @@ fn an_error_detail_is_escaped_in_chat_and_admin_errors() {
         assert!(text.contains("\\u202e"), "{text}");
     }
 }
+
+/// A frame that does not decode is reported with serde's message, which quotes the offending
+/// text after JSON decoding: from a compromised peer that can be raw escape sequences.
+#[test]
+fn a_frame_error_is_escaped() {
+    let bad = r#"{"v":1,"id":1,"final":true,"msg":{"kind":"\u001b[2J\u202e"}}"#;
+    let error = serde_json::from_str::<proto::Envelope>(bad).unwrap_err();
+    for text in [
+        ChatError::Frame(proto::FrameError::Json(
+            serde_json::from_str::<proto::Envelope>(bad).unwrap_err(),
+        ))
+        .to_string(),
+        AdminError::Frame(proto::FrameError::Json(error)).to_string(),
+    ] {
+        clean(&text);
+        assert!(text.contains("\\u001b"), "{text}");
+    }
+}