hero is a composition over section

Acceptance Criteria

• A composed hero definition declares align, the split attributes, content-place, height and aspect, and forwards them to its section
• It declares defaults: { width: full, elevation: flush, prominence: display } and writes guest-fit="bleed" on its section
• It reads no heading as an eyebrow (ADR-046), and a second leading heading is body rather than dropped (BUG-047)
• Rendered beside the plugin hero for every gallery fixture, light and dark, including cover; every difference is listed and explained
• actions.css in skeleton and Lumina sets the button-size custom properties from the enclosing section's data-prominence: display and prominent give today's hero size (0.7rem 1.75rem at --rf-text), and anything else gives today's cta size (SPEC-160 D7)
• The size rules reach only an actions whose nearest enclosing rune carries the prominence, asserted with a card holding actions inside a display hero, which keeps default buttons
• The composed hero's buttons match the plugin hero's in size, with no hero.css
• The plugin hero is unchanged; replacing it is a later step, taken once the comparison is reviewed