feat: add documentation website (Docusaurus)

- 25 documentation pages covering Getting Started, User Guide, Developer Guide, and Reference
- Docusaurus with custom amber/gold theme matching the landing page branding
- GitHub Actions workflow to deploy landing page + docs to GitHub Pages
- Landing page at root, docs at /docs/ on hermes-agent.nousresearch.com
- Content extracted and restructured from existing repo docs (README, AGENTS.md, CONTRIBUTING.md, docs/)
- Auto-deploy on push to main when website/ or landingpage/ changes

website/docs/developer-guide/_category_.json

@@ -0,0 +1,8 @@
+{
+  "label": "Developer Guide",
+  "position": 3,
+  "link": {
+    "type": "generated-index",
+    "description": "Contribute to Hermes Agent — architecture, tools, skills, and more."
+  }
+}