Require quality checks and update contributor tooling

[gijzelaerr]

Summary

• Require Python lint, type checking, and C++ formatting jobs to pass.
• Make the editor subprocess test launch the active Python interpreter, so virtual environments work correctly.
• Update the documented Python minimum and the contributor build commands to match scikit-build-core and CMake.
• Replace obsolete tox commands with the Ruff checks used in CI.

The contributor-documentation changes overlap #497 and parts of #502; the tooling changes also touch work proposed in #503. These should be reconciled during review.

Validation

• Native build and full test suite passed locally.
• Pyright, Ruff lint and format, C++ formatting, and workflow YAML parsing passed locally.