The Python binding (kpy/): klammertext.Machine from a script

Assembled from klammertext-dev ed13dfaa5b7a.  kpy/klammertext.cpp is a
CPython extension module giving a Python script an instance of the
Machine class -- ktext in-process, set up through the same functions the
command uses.  Errors map one-to-one to Python exceptions under the C++
names; an @eval's Python exception is chained as __cause__.  Built by
make -C mac, found through PYTHONPATH (env/runtime.env sets it), tested
by tst/kpy_test.sh.  Three engine changes came with it: Error::message(),
set_command_state(), and the @eval error report carrying its traceback.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Uv7KWxafinDPraswEf4GsC

mac/Makefile

@@ -31,11 +31,12 @@ DEPFLAGS = -MMD -MP -MF $(@:.o=.d)
 	$(CXX) -c $(CPPFLAGS) $(CXXFLAGS) $(DEPFLAGS) $< -o $@
 
 # Default target
-.PHONY: all sks ref clean redo clang
+.PHONY: all sks ref kpy clean redo clang
 
 all : $(LIBRARY)
 	$(MAKE) sks
 	$(MAKE) ref
+	$(MAKE) kpy
 
 # Create lib directory
 $(LIBDIR):
@@ -60,6 +61,13 @@ sks :
 ref :
 	$(MAKE) -C $(K)/ref
 
+# kpy/ is the Python binding: a CPython extension module that links against
+# libklammertext.so and shares its class layouts, like the sks DSOs and
+# ref/.  A fourth consumer of the library, and neither a command nor a
+# klammer set.
+kpy :
+	$(MAKE) -C $(K)/kpy
+
 clean :
 	rm -f $(OBJECTS) $(DEPFILES) $(LIBRARY) *~