ansible: add reboot playbook and short hostname support

- Add reboot.yml playbook with rolling reboot (serial: 1)
  - Uses systemd reboot.target for NixOS compatibility
  - Waits for each host to come back before proceeding
- Update dynamic inventory to use short hostnames
  - ansible_host set to FQDN for connections
  - Allows -l testvm01 instead of -l testvm01.home.2rjus.net
- Update static.yml to match short hostname convention

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

ansible/README.md

@@ -64,6 +64,7 @@ Non-flake hosts are defined in `inventory/static.yml`:
 |----------|-------------|---------|
 | `run-upgrade.yml` | Trigger nixos-upgrade on hosts | `-l tier_prod` |
 | `restart-service.yml` | Restart a systemd service | `-l role_dns -e service=unbound` |
+| `reboot.yml` | Rolling reboot (one host at a time) | `-l tier_test` |
 | `provision-approle.yml` | Deploy Vault credentials (single host only) | `-l testvm01` |
 | `build-and-deploy-template.yml` | Build and deploy Proxmox template | (no limit needed) |
 
@@ -82,6 +83,9 @@ nix develop -c ansible-playbook ansible/playbooks/provision-approle.yml -l testv
 
 # Build and deploy Proxmox template
 nix develop -c ansible-playbook ansible/playbooks/build-and-deploy-template.yml
+
+# Rolling reboot of test hosts (one at a time, waits for each to come back)
+nix develop -c ansible-playbook ansible/playbooks/reboot.yml -l tier_test
 ```
 
 ## Excluding Flake Hosts