docs: remove legacy docs/ directory — all content migrated to website

Removed 10 markdown files (~4,200 lines) that have been fully migrated,
restructured, and accuracy-audited on the docs site at
hermes-agent.nousresearch.com/docs/

Left docs/README.md as a pointer to the website.
Updated CONTRIBUTING.md file tree reference.

CONTRIBUTING.md

@@ -170,7 +170,7 @@ hermes-agent/
 ├── skills/                   # Bundled skills (copied to ~/.hermes/skills/ on install)
 ├── environments/             # RL training environments (Atropos integration)
 ├── tests/                    # Test suite
-├── docs/                     # Additional documentation
+├── website/                  # Documentation site (hermes-agent.nousresearch.com)
 │
 ├── cli-config.yaml.example   # Example configuration (copied to ~/.hermes/config.yaml)
 └── AGENTS.md                 # Development guide for AI coding assistants