Unreal build configurations (Development / Shipping / …)

Build Solution now opens a configuration picker (Development Editor,
Development, DebugGame, Shipping) and passes /p:Configuration=<cfg>
/p:Platform=Win64 to MSBuild, which drives UnrealBuildTool for the chosen
config. Streams into the same minimizable build overlay.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/p4.ts

@@ -76,7 +76,7 @@ export const p4 = {
   openInExplorer: (target: string) => invoke<void>("open_in_explorer", { target }),
   findUproject: (scope: string) => invoke<string>("find_uproject", { scope }),
   findSln: (scope: string) => invoke<string>("find_sln", { scope }),
-  buildSln: (path: string) => invoke<string>("build_sln", { path }),
+  buildSln: (path: string, config: string) => invoke<string>("build_sln", { path, config }),
   launchFile: (path: string) => invoke<void>("launch_file", { path }),
   openInVscode: (depot: string) => invoke<void>("open_in_vscode", { depot }),
   readDepot: async (depot: string): Promise<ArrayBuffer> => {