build: dendritic flake, devShell and crate skeleton

nix/package.ulu.nix

@@ -0,0 +1,40 @@
+{ ... }:
+{
+  perSystem =
+    { pkgs, lib, ... }:
+    {
+      packages.default = pkgs.rustPlatform.buildRustPackage {
+        pname = "valw";
+        version = "0.1.0";
+
+        src = lib.cleanSourceWith {
+          src = ../.;
+          filter =
+            path: _type:
+            !(builtins.elem (baseNameOf path) [
+              ".direnv"
+              ".jj"
+              "result"
+              "target"
+            ]);
+        };
+
+        cargoLock.lockFile = ../Cargo.lock;
+
+        nativeBuildInputs = [ pkgs.pkg-config ];
+        buildInputs = [
+          pkgs.libxkbcommon
+          pkgs.wayland
+        ];
+
+        # Tests run through `nix flake check` instead.
+        doCheck = false;
+
+        meta = {
+          description = "macOS-style screenshots for niri";
+          mainProgram = "valw";
+          platforms = lib.platforms.linux;
+        };
+      };
+    };
+}