feat(site): shrink Antidote, faithful two-bar Live Mode demo

Antidote (task b): drop the duplicated pattern tabs (content lives on
/anti-patterns for the full list). Keep the Gallery of Shame as the
signature visual and add a "Browse the full catalog" link underneath.
Section is roughly 40% shorter vertically.

Live Mode demo (task faithful): rewrite to match the real picker flow
one-for-one. Now two separate bars:
- Global bar: dark pill, bottom of the frame, persistent for the
  whole session. / + Pick (active) + Detect + DESIGN.md + divider + ✕.
- Contextual bar: LIGHT paper-backed pill that floats above the
  picked element, mirroring buildConfigureRow() in live-browser.js.
  Dark command pill, transparent input, ×N count, magenta Go button.
  Morphs through configure → generating (spinner) → cycling (prev /
  counter / next / discard / Accept) → accepted (green ✓ written to
  source).

Contextual bar positions itself below the target when space allows,
else above. New JS positionCtx() mirrors the real positionBar()
logic. prefers-reduced-motion still freezes on a representative
"cycling, variant 3" still.

Timeline unchanged in steps but step captions updated to match the
new two-bar split ("Contextual bar appears." etc.).

public/css/main.css

@@ -2274,6 +2274,7 @@ code {
   display: flex;
   gap: var(--spacing-xl);
   align-items: stretch;
+  justify-content: center;
   margin-bottom: var(--spacing-xl);
 }