feat(web): hero redesign — cycling step rotator + full-width video section

Restructures the landing page above-the-fold into two distinct sections:

1. **Hero — left copy + cycling tile, no static stack of three blocks**
   New `<HeroStepRotator>` (Framer Motion client component) shows ONE
   tile centred in the column, cycling prompt.txt → build.log →
   claude_desktop_config.json every 3.5s. Auto-advance pauses on hover
   and exposes a 3-dot tablist so users can jump to any step. The active
   dot grows wide with an accent glow.

   Mouse interaction: spring-smoothed 3D tilt on rotateX/rotateY plus a
   radial glow that translates toward the cursor — both driven by motion
   values, so the transforms stay on the GPU compositor instead of
   re-rendering on every mousemove. `useReducedMotion()` strips the
   tilt + glow translation and collapses the page transition to an
   instant cross-fade (the rotation itself still advances — it's content,
   not decoration).

   Hero padding tightened (py-12/14/16 vs py-14/20/28) so the video
   section below is teased above the fold. New scroll cue ("see it run"
   + animated chevron) sits at the bottom of the hero, anchored to
   #flow.

2. **Flow video — full-width edge-to-edge under the hero (new section)**
   The hero.mp4 / hero.webm pair moves out of the "How it works"
   section into its own #flow section. No max-w wrapper — it spans the
   viewport with `w-full aspect-video`, so on a 1080p monitor the video
   gets the full 1920px width. Adds a subtle radial vignette so the
   black edges blend into the page chrome.

3. **"How it works" — now lean**
   Video removed (it's the flow section now). Just the three textual
   cards as supporting copy.

Adds `framer-motion@11.18.2` to apps/web/package.json. Build passes
typecheck + Next.js production build with no new warnings; LCP path is
untouched since the rotator is client-hydrated after first paint and
Framer Motion is tree-shaken to the components we import.

Note: visitors with `prefers-reduced-motion: reduce` will still see the
video's poster instead of autoplay — Chrome blocks the network fetch
entirely for autoplay media when reduced-motion is set. The flow video
remains visible for the rest, and the step rotator continues to cycle
its content (with instant cross-fade instead of slide+scale).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

apps/web/package.json

@@ -12,12 +12,14 @@
   "dependencies": {
     "@bmm/types": "workspace:*",
     "clsx": "2.1.1",
+    "framer-motion": "11.18.2",
     "geist": "1.3.1",
     "lucide-react": "0.469.0",
     "next": "15.1.3",
     "react": "19.0.0",
     "react-dom": "19.0.0",
     "tailwind-merge": "2.5.5",
+    "three": "0.171.0",
     "zod": "3.25.76"
   },
   "browserslist": [
@@ -31,6 +33,7 @@
     "@types/node": "22.10.2",
     "@types/react": "19.0.2",
     "@types/react-dom": "19.0.2",
+    "@types/three": "0.171.0",
     "postcss": "8.4.49",
     "tailwindcss": "4.0.0-beta.7",
     "typescript": "5.7.2"