Simplify CI pipeline and gh-pages deployment

[G-Fourteen]

Summary

• replace the previous multi-step helpers with a single GitHub Actions job that installs dependencies, runs pytest, builds the static assets, and deploys them
• remove the bespoke composite action and Python helper scripts that previously orchestrated installs, testing, and summary generation
• publish the site by force-pushing the built dist/ output to the gh-pages branch so only one workflow run handles the build and deploy

Testing

• pytest

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https://chatgpt.com/codex/tasks/task_b_69060c6259448329b8df8848e1a380de