Update to ANTLR 4.13 and add Python 3.13 support

[brianatdetections]

Summary

This PR updates the STIX Pattern Validator to use ANTLR 4.13.x and adds Python 3.13 support.

Changes

• ANTLR Runtime: Updated antlr4-python3-runtime dependency from ~=4.9.0 to ~=4.13.0
• Parser Regeneration: Regenerated all 12 parser files across 3 locations with ANTLR 4.13.2
• Python 3.13: Added to test matrix, classifiers, and GitHub Actions workflow
• Automation: Added scripts/regenerate_grammars.sh for easy grammar regeneration
• Documentation: Fixed ANTLR generation docs to use Python3 instead of Python2
• GitHub Actions: Updated to latest action versions (checkout@v4, setup-python@v5, codecov@v4)
• Version: Bumped to 2.1.0

Breaking Change Note

The upstream grammar now requires timestamp literals with the t prefix for STARTSTOP qualifiers (e.g., START t'2024-01-01T00:00:00Z' instead of START '2024-01-01T00:00:00Z'). This aligns with the current STIX 2.1 specification. The v20 inspector and tests have been updated accordingly.

Test Plan

• All 177 existing tests pass
• Pre-commit hooks pass (flake8, isort, trailing whitespace)
• Packaging validation passes (twine check)
• Tested on Python 3.12

Files Changed

Category	Files
Grammar (regenerated)	12 files (4 per location × 3 locations)
Configuration	setup.py, setup.cfg, tox.ini, MANIFEST.in
CI/CD	.github/workflows/python-ci-tests.yml
Documentation	docs/conf.py, docs/developers.rst, CHANGELOG.rst
Code	stix2patterns/v20/inspector.py
Tests	stix2patterns/test/v20/test_inspector.py
New	scripts/regenerate_grammars.sh

CLA

I have signed the Individual Contributor License Agreement.

---

🤖 Generated with Claude Code

[CLAassistant]

All committers have signed the CLA.

[brianatdetections]

recheck

[brianatdetections]

@ejratl @clenk @chisholm @JasonKeirstead @sparrell

Hi maintainers! This PR updates ANTLR to 4.13.2 and adds Python 3.13 support.

Key improvements over the existing PR #96:

• Newer ANTLR version (4.13.2 vs 4.13.1)
• Includes automated regeneration script (scripts/regenerate_grammars.sh)
• Updates ALL grammar directories (including shared stix2patterns/grammars/)
• Adds Python 3.13 to test matrix and CI
• Fixes v20 inspector for grammar API changes (TimestampLiteral)
• Updates GitHub Actions to latest versions (checkout@v4, setup-python@v5)

All 177 tests pass, CLA is signed, and CI is green. Would appreciate a review when you have time. Happy to address any feedback!

[vEpiphyte]

@brianatdetections Nice work! It would probably be best to include Python 3.14 as a supported target as well; since that would be one more package pulled into support for the modern world. I haven't looked to see about antlr4 version support for 3.14 is; so that could be a issue there.

[ejratl]

This is great work! Thank you @brianatdetections The large grammar files make it a bit hard to review - since they are generated, I wonder if it would be possible to omit them and have users generate them on their own - would that be too much of a usability hit? I will work on reviewing this and merge after I have done so.

[vEpiphyte]

The generated bindings should be reproducible; so they should be able to be independently generated from the input .g4 files and shown to be the same.

Asking users to generate them from g4 files would require them to have java and the appropriate antlr jar available to build them with; which could be a tall order for a python package to ask for.