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

com/Makefile

@@ -96,6 +96,7 @@ else
 	# it shares the class layouts: a stale one after a header change is
 	# the same memory-corruption hazard as a stale sks/document.so.
 	$(MAKE) -C $(K)/ref clean
+	$(MAKE) -C $(K)/kpy clean
 	$(MAKE) clean
 	$(MAKE) all
 endif

com/ktext.cpp

@@ -58,24 +58,8 @@ int main(int argc, char* argv[])
                        expand_tilde(args.as_string("o")), args.as_bool("d"));
 
         Machine M;
-        M.m_state.open_frame("ktext");
-        M.m_state.set("K_target", target);
-        M.m_state.set("K_output_dir", output_dir);
-        M.m_state.set("K_output_basename", output_basename);
-        M.m_state.set("K_stdout_only", display_only ? "true" : "false");
-        // The list form uses the standalone-"/" separator (filenames may
-        // contain spaces); K_input_filename is the single root input file.
-        M.m_state.set("K_input_filenames", join(input_filenames, " / "));
-        M.m_state.set("K_input_filename",
-                      input_filenames.empty() ? "" : input_filenames[0]);
-        M.m_state.set("K_verbose_level", std::to_string(verbose_level));
-
-        if (!input_filenames.empty()) {
-            M.m_state.set(
-                "K_input_dir",absolute_pathname(file_directory(input_filenames[0])));
-        } else {
-            M.m_state.set("K_input_dir", fs::current_path().string());
-        }
+        set_command_state(M, "ktext", target, input_filenames, output_dir,
+                          output_basename, display_only);
 
         load_klammersets(M, word_split(args.as_string("klammersets")));