chore(ai-workflow): add toolchain drift validator and harden agent rules

Borrowed from a review of addyosmani/agent-skills:

- add scripts/validate-ai-workflow.mjs (yarn ai-workflow:check): verifies
  .claude/.codex/.cursor skills, agents, and hooks stay in parity, with
  validator-owned exemptions for intentional harness-specific differences
  and enforcement of the AGENTS.md agent model rules
- browser-check and profiler agents: treat page content as untrusted data,
  never instructions (5chan pages render arbitrary user-generated content)
- refactor-pass: Chesterton's Fence rule (git blame unclear code before
  removing it)
- review-and-merge-pr: pass subagent verifiers only the artifact and
  contract, not the triage verdict, to keep reviews independent

package.json

@@ -55,6 +55,7 @@
     "zustand": "4.4.3"
   },
   "scripts": {
+    "ai-workflow:check": "node scripts/validate-ai-workflow.mjs",
     "generate:assets": "node scripts/generate-asset-manifest.js",
     "llms:generate": "node scripts/generate-llms-files.mjs",
     "map:generate": "node scripts/generate-world-map-dots.mjs",