Supplies the offline plotly.js bundle for the new canvas backend. The
GUI CI job now installs the gui extra so the Qt/WebEngine tests run
instead of being import-skipped.
Reconstructs the workflow stripped during the tree copy to match the
meta-gates: separate type job, headless command over
tests/unit+tests/services, and dedicated GUI / integration jobs.
Tool versions pinned to the pre-commit revisions (ruff 0.4.4,
mypy 1.10.0) so CI and local hooks agree.
