Add JS toolchain: TypeScript, ESLint, Prettier, Vitest

package.json declares the project as ESM with NodeNext module resolution,
exposing dist/index.js as the library entry and dist/bin/quack.js as the
CLI binary. Dev dependencies are pinned to exact versions (yarn.lock holds
the integrity hashes per repo policy on hash-pinned external references).
Adds a placeholder src/index.ts and a single smoke test so make check is
not a no-op.

src/index.ts

@@ -0,0 +1 @@
+export const VERSION = "0.0.0";