feat: disko OS-disk layout + nixos-anywhere install flow

- add disko input; jupiter partitions/formats OS disk declaratively
- hardware-configuration.nix carries kernel modules only (disko owns fileSystems)
- data disk stays a plain unformatted mount, out of disko
- vbox unchanged (virtualbox-image supplies its own disk)
- README: nixos-anywhere remote install + daily rebuild loop

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

jupiter/hardware-configuration.nix

@@ -1,14 +1,13 @@
-# PLACEHOLDER — do not use as-is.
+# PLACEHOLDER — replace on the real machine.
 #
-# Generate the real file ON the ZimaBlade after booting the NixOS installer:
+# disko (disk-config.nix) owns the OS-disk filesystems, so this file should
+# only carry kernel modules + platform. Get the real values from the target:
 #
-#   sudo nixos-generate-config --root /mnt
+#   # during install, or via nixos-anywhere --generate-hardware-config:
+#   sudo nixos-generate-config --no-filesystems --root /mnt
 #
-# then copy /mnt/etc/nixos/hardware-configuration.nix over this file.
-# It contains machine-specific disk UUIDs, filesystems, and kernel modules.
-#
-# The block below is a minimal example so `nix flake check` does not fail on a
-# workstation. REPLACE it entirely with the generated output.
+# `--no-filesystems` omits the fileSystems.* blocks (disko provides them).
+# Copy the generated file over this one. Keep the imports/kernel-module lines.
 { config, lib, pkgs, modulesPath, ... }:
 
 {
@@ -19,22 +18,8 @@
   boot.kernelModules = [ ];
   boot.extraModulePackages = [ ];
 
-  # Example root — replace UUID with real value from generated config.
-  fileSystems."/" = {
-    device = "/dev/disk/by-label/nixos";
-    fsType = "ext4";
-  };
-
-  fileSystems."/boot" = {
-    device = "/dev/disk/by-label/BOOT";
-    fsType = "vfat";
-  };
-
-  # Example NAS data mount. Point at your storage disk/pool.
-  # fileSystems."/mnt/data" = {
-  #   device = "/dev/disk/by-label/data";
-  #   fsType = "ext4";
-  # };
+  # NO fileSystems here — disko defines "/" and "/boot" (see disk-config.nix).
+  # The NAS data mount lives in configuration.nix.
 
   swapDevices = [ ];