Use active interpreter for module entrypoint version test

[srichs]

Motivation

• Replace the hard-coded python executable in the module-entrypoint version test so the subprocess invocation uses the same interpreter running the tests and avoids platform-specific resolution failures.

Description

• Add import sys and change the subprocess invocation in tests/test_cli.py::test_module_entrypoint_supports_version_flag to use sys.executable instead of the literal "python".

Testing

• Ran pytest -q tests/test_cli.py::test_module_entrypoint_supports_version_flag tests/test_cli.py::test_version_flag_prints_version which passed.
• Ran pytest -q which completed successfully with all tests passing (93 passed).

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Codex Task