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.

mac/eval_python.h

@@ -5,6 +5,18 @@
 
 #include "machine.h"
 
+// Where a klammer set's Python may speak.  Embedded Python's own stdout is
+// nowhere a user looks: its buffer is never flushed (no Py_Finalize), so on
+// a pipe or a file a print() vanished, and on a terminal it landed in the
+// document's stream.  Under a command, Eval_python routes it to the engine's
+// log instead: K_log(level, text) is a builtin every module sees (kutil.msg
+// uses it), and sys.stdout is replaced by a stream that logs each line at
+// level 1 -- stderr under -v, silent otherwise, never the document (the
+// output policy in CLAUDE.md).  The switch is ON for the commands
+// (set_verbose_level) and OFF for the Python binding, where sys.stdout is
+// the host script's own and must not be touched.
+void set_python_output_to_log(bool on);
+
 class Eval_python
 {
 public: