Add auto-install for missing prerequisites

- New lib/prereqs.sh: detects distro (Arch, Debian/Ubuntu, RHEL/Fedora,
  openSUSE) and installs git + podman/docker if missing
- Podman preferred over docker; user chooses if neither present
- Docker install also enables systemd service and adds user to docker group
- README updated: prereqs table now shows auto-install support

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

README.md

@@ -23,12 +23,16 @@ Open in devcontainer → start Context Studio → talk to your agent team.
 
 ## 📋 Prerequisites
 
-| | Tool | Purpose |
+| | Tool | Notes |
 |---|------|---------|
-| 🔀 | `git` | Clone repos |
-| 🐳 | `docker` or `podman` | Run devcontainer |
-| 🔑 | SSH key → `github.com` | Access context-studio-core |
-| 🗝️ | `ANTHROPIC_API_KEY` | Claude agents |
+| 🔀 | `git` | Auto-installed if missing |
+| 🐳 | `podman` _(preferred)_ or `docker` | Auto-installed if missing |
+| 🔑 | SSH key → `github.com` | Must be set up manually |
+| 🗝️ | `ANTHROPIC_API_KEY` | Must be set in your environment |
+
+**Auto-install supported on:** Arch · Debian/Ubuntu · RHEL/Fedora · openSUSE
+
+> The wizard detects your distro and installs `git` and `podman`/`docker` automatically if they are missing. SSH key and API key must be set up by you.
 
 ---