Learner launch blockers

A short release with one job: clear what the launch review found across the learner surface.

The launch review, closed

One pass over everything the pre-release review found on the learner surface — the dashboard, the path pages, the lesson player and the achievements screens. Nothing new was added; the point of the release was to leave the surface honest before anyone was invited onto it.

Also in this release

Fixed

• The launch blockers and bugs found across the learner surface, from the dashboard through the player.

Changed

• The build now checks out and authenticates with current tooling, so the pipeline stops warning on every run.