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>

scripts/update_quaternions_deps.sh

@@ -0,0 +1,51 @@
+#!/usr/bin/env bash
+# Update Quaternions registry dependencies and run the full safety gate.
+#
+# Usage:
+#   scripts/update_quaternions_deps.sh <klondike_version> <card_game_version>
+#
+# Example:
+#   scripts/update_quaternions_deps.sh 0.3.1 0.4.1
+#
+# This script updates Cargo.lock to the requested versions (within the semver
+# ranges already declared in Cargo.toml), then runs the project's required
+# verification steps plus deterministic replay checks.
+set -euo pipefail
+
+if [ "$#" -ne 2 ]; then
+  echo "usage: $0 <klondike_version> <card_game_version>"
+  exit 2
+fi
+
+KLONDIKE_VERSION="$1"
+CARD_GAME_VERSION="$2"
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+
+cd "$REPO_ROOT"
+
+echo ">>> Quaternions registry:"
+echo "    https://git.aleshym.co/api/packages/Quaternions/cargo/"
+echo
+echo ">>> Review upstream release notes / changelogs before proceeding:"
+echo "    - https://git.aleshym.co/Quaternions/card_game"
+echo "    - https://git.aleshym.co/Quaternions/klondike"
+echo
+
+echo ">>> Updating lockfile to klondike=$KLONDIKE_VERSION card_game=$CARD_GAME_VERSION"
+cargo update -p klondike --precise "$KLONDIKE_VERSION"
+cargo update -p card_game --precise "$CARD_GAME_VERSION"
+
+echo ">>> Verifying dependency graph"
+cargo tree -p solitaire_core --depth 2 | cat
+
+echo ">>> Running workspace tests"
+cargo test --workspace
+
+echo ">>> Running workspace clippy"
+cargo clippy --workspace -- -D warnings
+
+echo ">>> Running deterministic replay / debug-api smoke checks"
+cargo test -p solitaire_wasm debug_snapshot_exposes_replayable_seed_and_history -- --exact
+cargo test -p solitaire_wasm debug_api_autonomous_seed_batch_smoke -- --exact
+
+echo ">>> Quaternions dependency upgrade gate passed"