fix(install): survive the live ISO offline and its non-interactive bash

Found by running the unattended install in an offline QEMU VM:
- compgen is missing from nixpkgs' non-interactive bash (the package
  shebang) — replaced with plain glob tests in hardware-db and prewipe
- disko's eval resolves <nixpkgs> via NIX_PATH (a dead channel on the
  ISO) and tried channels.nixos.org — export NIX_PATH to the pinned
  nixpkgs source and point the flake registry at an empty baked file
- lock nomarchy by path (the source the ISO carries) instead of
  git+https: git inputs clone even when narHash is known, which kills
  offline installs; `original` keeps the forge URL so a later
  `nix flake update` re-resolves normally. Works from dirty-tree ISOs too.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

flake.nix

@@ -44,16 +44,19 @@
         hardwareModuleNames = pkgs.writeText "nixos-hardware-modules.txt"
           (nixpkgs.lib.concatStringsSep "\n"
             (builtins.attrNames nixos-hardware.nixosModules));
+        nixpkgsPath = nixpkgs.outPath;
         flakeUrl = "git+${gitUrl}";
+        # Future updates re-resolve from the forge (original); the install
+        # itself resolves from the ISO store (locked = path) — fully
+        # offline, even from a dirty-tree ISO.
         originalNode = { type = "git"; url = gitUrl; };
         lockedNode = {
-          type = "git";
-          url = gitUrl;
-          rev = self.rev or null; # null on a dirty tree → installer needs network
+          type = "path";
+          path = self.outPath;
           narHash = self.narHash;
           lastModified = self.lastModified or 0;
-          revCount = self.revCount or 0;
         };
+        rev = self.rev or null;
       };
     in
     {