nix: Add nix runs

Signed-off-by: Naomi Roberts <[e-mail]>

.tangled/workflows/test-api.yaml

···
 steps:
   - name: test api
     command: |
-      cd api
-      nix develop --command bash -c 'gleam test'
+      nix run .#test-api

.tangled/workflows/test-web.yaml

···
 
 steps:
   - name: test website
-    environment:
-      KATARI_API_DOCS: "true"
     command: |
-      cd web
-      nix develop --command bash -c 'gleam test'
+      nix run .#test-web

api/README.md

···
 
 ## Running
 ```bash
+cd api
 gleam run
+```
+
+### Nix
+
+```bash
+nix run .#api
 ```
 
 If using a non-standard location for your SRD directory, this can be specified with the `KATARI_SRD_PATH` environment variable. It will default to `../srd` otherwise.

flake.nix

···
         ];
       };
     });
+    apps = forEachSupportedSystem ({pkgs}: {
+      api = {
+        type = "app";
+        program = toString (pkgs.writeShellScript "run-api" ''
+          rootDir=$(jj --ignore-working-copy root || git rev-parse --show-toplevel) || (echo "error: can't find repo root?"; exit 1)
+          cd "$rootDir/api"
+          export KATARI_SRD_PATH="$rootDir/srd"
+          ${pkgs.gleam}/bin/gleam run
+        '');
+      };
+      web = {
+        type = "app";
+        program = toString (pkgs.writeShellScript "run-web" ''
+          rootDir=$(jj --ignore-working-copy root || git rev-parse --show-toplevel) || (echo "error: can't find repo root?"; exit 1)
+          cd "$rootDir/web"
+          export KATARI_SRD_PATH="$rootDir/srd"
+          export KATARI_API_DOCS=true
+          ${pkgs.gleam}/bin/gleam run
+        '');
+      };
+      test-api = {
+        type = "app";
+        # TODO: Check if env vars are already set
+        program = toString (pkgs.writeShellScript "test-api" ''
+          rootDir=$(jj --ignore-working-copy root || git rev-parse --show-toplevel) || (echo "error: can't find repo root?"; exit 1)
+          cd "$rootDir/api"
+          export KATARI_SRD_PATH="$rootDir/srd"
+          ${pkgs.gleam}/bin/gleam test
+        '');
+      };
+      test-web = {
+        type = "app";
+        program = toString (pkgs.writeShellScript "test-web" ''
+          rootDir=$(jj --ignore-working-copy root || git rev-parse --show-toplevel) || (echo "error: can't find repo root?"; exit 1)
+          cd "$rootDir/web"
+          export KATARI_SRD_PATH="$rootDir/srd"
+          export KATARI_API_DOCS=true
+          ${pkgs.gleam}/bin/gleam test
+        '');
+      };
+    });
   };
 }

web/README.md

···
 
 ## Running
 ```bash
+cd web
 gleam run
+```
+
+### Nix
+```bash
+nix run .#web
 ```
 
 Set the `KATARI_API_DOCS` environment variable to `true` to enable them.