feat(e2e): add Playwright browser test suite for web routes

solitaire_server/e2e/:
- smoke.spec.js: verifies /play-classic loads, exposes window.__FERROUS_DEBUG__
  bridge, keyboard parity (Space=draw, U=undo), debug failure report, and
  replay payload builder exports schema-v2 moves.
- gameplay_review.spec.js: HUD/controls render check, stock-click + undo
  player flow, draw-mode toggle, autonomous play invariant batch, and
  cycle-detection regression guard.
- cycle_metrics.js: headless cycle-rate analysis tool; run via
  `npm run review:cycles` with configurable policy, game count, and
  thresholds. Regression gate baked into package.json scripts.
- playwright.config.js: targets the local server at http://localhost:8080.
- package.json / package-lock.json: @playwright/test 1.60.0.

.gitea/workflows/web-e2e.yml:
- Runs on pushes to solitaire_server/, solitaire_wasm/, solitaire_core/,
  or Cargo changes. Starts the server binary, waits for /health, runs
  the full Playwright suite, uploads test-results/ on failure.

docs/testing-architecture.md: documents the three-tier test strategy
  (unit → Playwright smoke → cycle regression) and the __FERROUS_DEBUG__
  bridge contract.

scripts/update_quaternions_deps.sh: helper to bump the Quaternions
  registry deps (klondike, card_game) by version and run the full
  safety gate including deterministic replay checks.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.gitea/workflows/web-e2e.yml

@@ -0,0 +1,49 @@
+name: Web E2E
+
+on:
+  push:
+    branches: [master]
+    paths:
+      - 'solitaire_server/web/**'
+      - 'solitaire_server/src/**'
+      - 'solitaire_server/e2e/**'
+      - 'solitaire_wasm/**'
+      - 'solitaire_core/**'
+      - 'Cargo.toml'
+      - 'Cargo.lock'
+      - '.gitea/workflows/web-e2e.yml'
+  workflow_dispatch:
+
+jobs:
+  web-e2e:
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+
+      - name: Install Rust
+        uses: dtolnay/rust-toolchain@stable
+
+      - name: Set up Node.js
+        uses: actions/setup-node@v4
+        with:
+          node-version: '20'
+          cache: 'npm'
+          cache-dependency-path: solitaire_server/e2e/package-lock.json
+
+      - name: Install e2e dependencies
+        working-directory: solitaire_server/e2e
+        run: npm ci
+
+      - name: Install Playwright browser
+        working-directory: solitaire_server/e2e
+        run: npx playwright install --with-deps chromium
+
+      - name: Run web e2e tests
+        working-directory: solitaire_server/e2e
+        run: npm test
+
+      - name: Run cycle regression gate
+        working-directory: solitaire_server/e2e
+        run: npm run review:cycles:regression