Wire .hbb-section to var(--hb-spacing-section) instead of hardcoded 6rem,
enabling hugoblox.layout.spacing (compact/comfortable/spacious) to take effect.
- Default to "spacious" (6rem) to preserve existing visual layouts
- Per-section override via design.spacing.padding still works (inline > class)
- Remove dead design.spacing frontmatter field from all templates
- Set correct layout.spacing token in each template's params.yaml
Closes#3314
George Cushen