docs: GitHub Pages site (index, connecting, architecture, installation)

Mirrors the proxy/sso-manager docs-site layout (Jekyll + Bootstrap
default layout, theta42 assets). Documents the username grammar, the TUI
picker, SFTP/WinSCP, how auth/access/key-injection/bridging work, and the
three install paths + the required sshPublicKey write-ACL.

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

docs/README.md

@@ -0,0 +1,24 @@
+# Documentation
+
+This directory is the GitHub Pages documentation site for the Jump Host project.
+
+**Live site:** https://theta42.github.io/jump-host/
+
+## Pages
+
+- `index.md` — overview and quick start
+- `connecting.md` — usage: the username grammar, the TUI picker, SFTP/WinSCP
+- `architecture.md` — how auth, access resolution, key injection, and bridging work
+- `installation.md` — Docker, bare-metal, and theta-env install; the LDAP write-ACL
+
+## Local preview
+
+```bash
+gem install jekyll bundler
+cd docs && jekyll serve
+# http://localhost:4000/jump-host/
+```
+
+## Updating
+
+Edit the markdown, push to `master`, and GitHub Pages rebuilds automatically.