label expected compile timing probe

docs/wasm-runtime-architecture.md

@@ -410,7 +410,10 @@ header free-functions are `inline`. The wasm backend exposes only declarations
 - **Log timeliness**: the base process line-buffers stdout before forking
   workers, the proactive compiler, and the WebSocket broker. This keeps each
   newline-terminated diagnostic attached to its actual journal time instead of
-  releasing an old block-buffered failure during unrelated later traffic.
+  releasing an old block-buffered failure during unrelated later traffic. The
+  private CLI timing gate labels its deliberate invalid-source request as
+  `UCE expected compile error`; public and unmarked CLI compilation failures
+  retain the ordinary `UCE compile error` operator signal.
 
 - **WebSocket end-to-end**: a headless client performs a raw WS handshake to
   `:HTTP_PORT` with path `/site/tests/websockets.ws.uce` (self-resolving