Link the product wiki and guidance docs from the README

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

README.md

@@ -7,6 +7,17 @@ each other's inventory, customers, or revenue.
 
 Authentication is HTTP **Basic auth**, as requested, scoped per tenant.
 
+## Documentation
+
+- **[Product wiki](docs/wiki/README.md)** — overview, domain model, features,
+  roles & access, API reference, glossary
+- **[CLAUDE.md](CLAUDE.md)** / **[AGENTS.md](AGENTS.md)** — guiding principles
+  for developers and AI agents
+- **[SECURITY.md](SECURITY.md)** · **[GOVERNANCE.md](GOVERNANCE.md)** ·
+  **[CONTRIBUTING.md](CONTRIBUTING.md)** — the rules
+- **[TESTING.md](TESTING.md)** · **[qa/README.md](qa/README.md)** — test suites
+  and the AI-assisted QA workflow
+
 ---
 
 ## Prerequisites