A klammer set's Python speaks through the log

Assembled from development commit d5f9c20b94b3. Since 5c29da5: a print() in
@eval, or in any Python a klammer set runs, is a log line -- on the
error stream under the command's name at -v 1, silent otherwise, never
in the document -- and K_log(level, text) is the builtin behind it; a
Python script using the binding keeps its own stdout. Previously such
output was lost, or on a terminal landed in the document.

sks/kutil/kutil.py

@@ -1,5 +1,6 @@
 import os
 import re
+import sys
 import inspect
 import html_util
 from html_util import E
@@ -14,9 +15,18 @@ def blue_text(text):
 def red_text(text):
       return f"\033[31m{text}\033[0m"
 
-def msg(text=""):
+def msg(text="", level=1):
+    """A message from the klammer set: the engine's log (K_log, a builtin
+    under ktext), shown at -v LEVEL or higher on stderr, never in the
+    document.  Outside a Machine (a module run by hand) it goes to stderr.
+    Until 2026-09-25 this was a print(): embedded Python's stdout, which no
+    user ever saw."""
     frame = inspect.currentframe().f_back
-    print(blue_text(f"[{os.path.basename(frame.f_code.co_filename)}:{frame.f_lineno}]"), text)
+    where = f"[{os.path.basename(frame.f_code.co_filename)}:{frame.f_lineno}]"
+    try:
+        K_log(level, f"{where} {text}")
+    except NameError:
+        print(where, text, file=sys.stderr)
 
 
 def escape(s):