[RT-E10] Docs and canon are reconciled, and the remaining divergences from upstream are recorded #489

Part of #350, the quality-refactoring roadmap (road to 1.0, step 3).

Goal: Docs and canon are reconciled, and the remaining divergences from upstream are recorded.

Lane: Runtime. Status: todo.

Every PR of this epic starts its title with [RT-E10]. The finding issues it closes are linked as sub-issues; this issue closes when the epic's last PR merges and master CI is green.