wgt01: add dev-install flake app (build -> export -> set -> development/)

`nix run .#dev-install` runs build.py, export_mdl.py and make_set.py into
./build, then stages the loose .mdl/.wok/.set into ~/Documents/Neverwinter
Nights/development/ for toolset testing without packing a .hak. Replaces only
twu01* files there; keeps build/ for inspection. gitignore build/ + *.blend.

Verified: 40 .mdl + 40 .wok + twu01.set (CRLF intact) staged into development/.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

wgt01/flake.nix

@@ -58,6 +58,27 @@
             --python-exit-code 1 -- "$outdir" "$@"
         '';
       };
+
+      # One shot: build -> export -> .set, then stage the loose files into the
+      # toolset's development/ folder (no .hak). Work dir defaults to ./build.
+      mkdev = pkgs.writeShellApplication {
+        name = "wgt-dev-install";
+        runtimeInputs = [ blender py ];
+        text = ''
+          work="''${1:-$PWD/build}"
+          dev="$HOME/Documents/Neverwinter Nights/development"
+          mkdir -p "$work/mdl" "$dev"
+          blend="$work/westgate_urban_foundation_mvp.blend"
+          blender-4.0.2 --background --python ${gen}/build.py --python-exit-code 1 -- "$blend"
+          blender-4.0.2 --background "$blend" --python ${gen}/export_mdl.py --python-exit-code 1 -- "$work/mdl"
+          python ${gen}/make_set.py "$work/twu01.set"
+          # replace only our own prefix in development/, leave everything else alone
+          rm -f "$dev"/twu01_*.mdl "$dev"/twu01_*.wok "$dev"/twu01.set
+          cp "$work"/mdl/twu01_*.mdl "$work"/mdl/twu01_*.wok "$work"/twu01.set "$dev"/
+          n=$(find "$work/mdl" -name 'twu01_*.mdl' | wc -l)
+          echo "installed $n tiles + twu01.set -> $dev"
+        '';
+      };
     in
     {
       packages.${system}.default = build;
@@ -83,6 +104,10 @@
           type = "app";
           program = "${mkmdl}/bin/wgt-export";
         };
+        dev-install = {
+          type = "app";
+          program = "${mkdev}/bin/wgt-dev-install";
+        };
       };
 
       devShells.${system}.default = pkgs.mkShell {