docs: full mdBook site + GitHub Pages deploy; rewrite README as project front page

- docs/: an mdBook documentation site — thesis, architecture, measurement
  discipline, equivalence gates, agent loop, isolation/anti-reward-hacking,
  playbook, ROI, reproduce, roadmap, and the five case studies (pulled from
  their single source in results/ via {{#include}}). Builds clean (21
  pages).
- .github/workflows/docs.yml: builds mdBook and deploys to GitHub Pages on
  push to main (one-time setup: Settings → Pages → Source = GitHub Actions).
- README.md: rewritten as the project front page — the thesis, the verified
  results table, layout, quick start, how it stays honest, links to the
  book. Replaces the stale Phase-0-era text.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EcKPWQ3MQD4NdEHwar96u2

.github/workflows/docs.yml

@@ -0,0 +1,53 @@
+name: docs
+
+# Builds the mdBook site in docs/ and deploys it to GitHub Pages.
+# One-time setup: repo Settings → Pages → Source = "GitHub Actions".
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - "docs/**"
+      - ".github/workflows/docs.yml"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+  pages: write
+  id-token: write
+
+# Allow one concurrent deployment; don't cancel an in-progress prod deploy.
+concurrency:
+  group: pages
+  cancel-in-progress: false
+
+jobs:
+  build:
+    runs-on: ubuntu-latest
+    env:
+      MDBOOK_VERSION: "0.4.40"
+    steps:
+      - uses: actions/checkout@v4
+      - name: Install mdBook
+        run: |
+          mkdir -p "$HOME/.local/bin"
+          url="https://github.com/rust-lang/mdBook/releases/download/v${MDBOOK_VERSION}/mdbook-v${MDBOOK_VERSION}-x86_64-unknown-linux-gnu.tar.gz"
+          curl -sSL "$url" | tar -xz -C "$HOME/.local/bin"
+          echo "$HOME/.local/bin" >> "$GITHUB_PATH"
+      - name: Build
+        run: mdbook build docs
+      - name: Upload artifact
+        uses: actions/upload-pages-artifact@v3
+        with:
+          path: docs/book
+
+  deploy:
+    needs: build
+    runs-on: ubuntu-latest
+    environment:
+      name: github-pages
+      url: ${{ steps.deployment.outputs.page_url }}
+    steps:
+      - name: Deploy to GitHub Pages
+        id: deployment
+        uses: actions/deploy-pages@v4