Correctly check whether Python is initialized in tortoize.cpp

[marcuscollins]

From CodeRabbit's review of the first PR:

Guard extract_python_executable_path() against uninitialized Python interpreter.

py::module::import("sys") at line 53 requires an initialized interpreter and GIL. This will crash in C++ unit tests (like tortoize-unit-test.cpp calling tortoize_calculate()), which trigger DataTable::instance() → constructor → extract_python_executable_path() without initializing Python.

Guard with Py_IsInitialized() before the import, or ensure the interpreter is initialized at all entrypoints that eventually trigger DataTable::instance().

fs::path extract_python_executable_path() {

• if (not Py_IsInitialized())

•   throw std::runtime_error("Python interpreter not initialized; initialize it before calling tortoize");
  

• py::gil_scoped_acquire gil;
  py::module py_sys = py::module::import("sys");
  py::str py_exec = py_sys.attr("executable");
  fs::path py_exec_path = fs::path(py_exec.caststd::string());
  return py_exec_path;
  }