refactor(deploy): generalize to any config, all params mandatory (no defaults)

README.md

@@ -67,14 +67,26 @@ an installer, partitions via disko, installs.
 Manual alternative (USB ISO): boot installer, `disko` the disk, then
 `nixos-install --flake .#jupiter`.
 
-## Rebuild after changes (the daily loop)
+## Deploy (the `./deploy` wrapper)
+
+All arguments mandatory — no default host, no default config.
 
 ```
-# from laptop, build + activate on jupiter over SSH:
-nixos-rebuild switch --flake .#jupiter \
-  --target-host darman@jupiter --use-remote-sudo
+./deploy kexec   <host>            # headless kexec into a RAM installer (RO-root box)
+./deploy install <config> <host>   # first install; wipes OS disk, ships host key
+./deploy switch  <config> <host>   # rebuild + activate on a running host
+./deploy boot|test <config> <host> # stage for next boot / activate without boot entry
 ```
-Rollback: `nixos-rebuild switch --rollback`, or pick a prior generation at boot.
+`<config>` is a `nixosConfigurations` name (`jupiter`, `vps`). Its pre-generated
+SSH host key lives at `~/.config/homelab/<config>/ssh_host_ed25519_key`.
+
+Examples:
+```
+./deploy switch jupiter jupiter.sol
+./deploy install vps 159.195.64.117
+```
+Rollback: `nixos-rebuild switch --rollback` on the host, or pick a prior
+generation at boot.
 
 ## Adding a service