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/user-guide/messaging/slack.md

@@ -0,0 +1,57 @@
+---
+sidebar_position: 4
+title: "Slack"
+description: "Set up Hermes Agent as a Slack bot"
+---
+
+# Slack Setup
+
+Connect Hermes Agent to Slack using Socket Mode for real-time communication.
+
+## Setup Steps
+
+1. **Create an app:** Go to [Slack API](https://api.slack.com/apps), create a new app
+2. **Enable Socket Mode:** In app settings → Socket Mode → Enable
+3. **Get tokens:**
+   - Bot Token (`xoxb-...`): OAuth & Permissions → Install to Workspace
+   - App Token (`xapp-...`): Basic Information → App-Level Tokens → Generate (with `connections:write` scope)
+4. **Configure:** Run `hermes gateway setup` and select Slack, or add to `~/.hermes/.env` manually:
+
+```bash
+SLACK_BOT_TOKEN=xoxb-...
+SLACK_APP_TOKEN=xapp-...
+SLACK_ALLOWED_USERS=U01234ABCDE    # Comma-separated Slack user IDs
+```
+
+5. **Start the gateway:**
+
+```bash
+hermes gateway
+```
+
+## Optional: Home Channel
+
+Set a default channel for cron job delivery:
+
+```bash
+SLACK_HOME_CHANNEL=C01234567890
+```
+
+## Required Bot Scopes
+
+Make sure your Slack app has these OAuth scopes:
+
+- `chat:write` — Send messages
+- `channels:history` — Read channel messages
+- `im:history` — Read DM messages
+- `files:write` — Upload files (audio, images)
+
+## Voice Messages
+
+Voice messages on Slack are automatically transcribed (requires `VOICE_TOOLS_OPENAI_KEY`). TTS audio is sent as file attachments.
+
+## Security
+
+:::warning
+Always set `SLACK_ALLOWED_USERS` to restrict who can use the bot. Without it, the gateway denies all users by default.
+:::