ci: add spdx workflow

[hyperfinitism]

This pull request adds a GitHub Actions workflow to check SPDX license header.

What's changed

• Add .github/workflows/spdx.yml — GitHub workflow that checks if each Python code includes an SPDX license header for MIT license
• Update *.py — Add MIT license SPDX header

Test

• No functional code changes.
• Confirmed the workflow passes (green) on this branch.

[coderabbitai]

Important

Review skipped

Auto reviews are disabled on this repository.

Please check the settings in the CodeRabbit UI or the .coderabbit.yaml file in this repository. To trigger a single review, invoke the @coderabbitai review command.

You can disable this status message by setting the reviews.review_status to false in the CodeRabbit configuration file.

---

Note

🎁 Summarized by CodeRabbit Free

Your organization is on the Free plan. CodeRabbit will generate a high-level summary and a walkthrough for each pull request. For a comprehensive line-by-line review, please upgrade your subscription to CodeRabbit Pro by visiting https://app.coderabbit.ai/login.

_{Comment @coderabbitai help to get the list of available commands and usage tips.}