fix(nix): migrate to fetchPnpmDeps and pnpmConfigHook

docs/plans/state.json

@@ -60,7 +60,7 @@
       "status": "completed",
       "date": "2026-02-16",
       "updated": "2026-02-16",
-      "summary": "Added a Nix flake/package that builds dist/ (including dist/gateway/ui adjacency) and an optional NixOS module (services.flynn) for systemd deployment. Follow-up fix switched package build from unavailable buildPnpmPackage to pnpm.fetchDeps + stdenv.mkDerivation and added flake.lock.",
+      "summary": "Added a Nix flake/package that builds dist/ (including dist/gateway/ui adjacency) and an optional NixOS module (services.flynn) for systemd deployment. Follow-up fixes switched package build from unavailable buildPnpmPackage to fetchPnpmDeps + stdenv.mkDerivation, migrated to pnpmConfigHook for current nixpkgs, and added flake.lock.",
       "files_created": [
         "flake.nix",
         "nix/package.nix",

nix/package.nix

@@ -23,8 +23,9 @@ pkgs.stdenv.mkDerivation rec {
       );
   };
 
-  pnpmDeps = pkgs.pnpm.fetchDeps {
+  pnpmDeps = pkgs.fetchPnpmDeps {
     inherit pname version src;
+    fetcherVersion = 1;
 
     # NOTE: Update this hash after the first `nix build` by copying the
   # "got: sha256-..." value from the error message.
@@ -33,7 +34,7 @@ pkgs.stdenv.mkDerivation rec {
 
   nativeBuildInputs = [
     pkgs.nodejs_22
-    pkgs.pnpm.configHook
+    pkgs.pnpmConfigHook
     pkgs.makeWrapper
     pkgs.python3
     pkgs.gnumake