W907 cool-slate consolidation: kill warm bleed + studio CTAs + demo-live rebuild

- public/warm-paper.css: define --paper-2/3 cool slate tokens (kills warm
  cream fallback bleed from index.html inline var(--paper-2, #f5f3ee))
- public/warm-paper.css: button + heading child font-weight: inherit cascade
  covers .btn, .button, .kolm-btn, .ks-btn, .cta, .pricing-cta, .nav-cta +
  span/b/strong/em/i/code/a children with !important
- public/warm-paper.css: .ks-btn--primary forced #1f2937 ink (kills green/teal
  drift); .ks-btn--secondary full definition
- public/studio.html: 3 stu-face__cta anchor buttons (Open Studio / Install
  the CLI / Read the TUI guide)
- public/studio/index.html: 3 shub-face__cta anchor buttons with .shub-face__row
  wrappers around <code> blocks
- public/demo-live.html: complete rebuild — light cool-slate default theme,
  chapter reorder (Capture > Compile > Verify > Run > Setup > Try it) leading
  with money shot not signup, receipt pane pre-populated (skeleton > partial
  > detail), stronger end-card hierarchy with primary CTA "Start your first
  compile" + "\$5 free credit, no card required"
- public/sw.js: CACHE_VERSION 136 > 137, slug w907-cool-slate-buttons-studio-
  ctas-demo-rebuild

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: sneaky-hippo