build: migrate manualChunks to function form for Vite 8 / Rolldown

Vite 8 switches the bundler to Rolldown, which no longer accepts the
object form of rollupOptions.output.manualChunks — it must be a function.
Convert it (same ndk/vendor split intent) and give tsconfig.node.json a
modern target/lib so vite.config.ts type-checks against String.includes.

.gitignore

@@ -48,3 +48,6 @@ skills-lock.json
 *.njsproj
 *.sln
 *.sw?
+
+# TypeScript incremental build info
+*.tsbuildinfo