Use lib.getExe for app outputs

- Switch flake app entries to `lib.getExe`
- Fix server package metadata field names

flake.nix

@@ -38,11 +38,11 @@
     apps = forAllSystems (system: rec {
       t3code-server = {
         type = "app";
-        program = "${self.packages.${system}.t3code-server}/bin/t3";
+        program = lib.getExe self.packages.${system}.t3code-server;
       };
       t3code-desktop = {
         type = "app";
-        program = "${self.packages.${system}.t3code-desktop}/bin/t3code";
+        program = lib.getExe self.packages.${system}.t3code-desktop;
       };
       default = t3code-desktop;
     });

packages/server/default.nix

@@ -94,8 +94,8 @@ in
       description = "t3 code web/server app";
       homepage = "https://github.com/pingdotgg/t3code";
       license = lib.licenses.mit;
-      mainprogram = "t3";
+      mainProgram = "t3";
       platforms = lib.platforms.unix;
-      sourceprovenance = with lib.sourcetypes; [fromsource];
+      sourceProvenance = with lib.sourceTypes; [fromSource];
     };
   })