Keep wide diagrams legible on narrow screens

The lifecycle and score diagrams use a 720-unit viewBox. Scaled to a
375px screen their 12.5px labels render around 6px, which is unreadable.
Each now scrolls inside its own overflow-x container with a minimum
width, so the diagram keeps its proportions instead of shrinking past
legibility.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>