Chemistry QPE course tracking issue

[HABER7789]

This issue tracks follow-up work identified while reviewing the Chemistry QPE course in #3568.

• "Start learning" is slow, and switching courses before it finishes redirects the learner to katas instead of the chosen course.
• Notify user if they are using the old workspace with older course content
• Keep generated notebook cell IDs stable when cell content changes.
• Find course.json without searching parent directories.
• Check the installed QDK/Chemistry version as part of environment validation.
• Decide whether output baking should remain Chemistry-specific or become shared course tooling.
• Improve exercises so hard coded answers do not pass.
• Require exercise checkers to run before an exercise is completed.
• Investigate notebook save prompts when auto save is enabled.
• Preserve or reapply the selected python kernel across units.
• Investigate notebook freezing while switching units or kernels.
• Explore a Copilot action for prose quiz questions. (stale if custom mime type quizzes take place)
• An authoring guide for the authors to create QDK Python learning courses
• Convert PNGs to SVGs