v6.1.2

Patch — packaging only. No API or behavior change.

Changed

• The ESM build now loads as true ESM. dist/esm is marked type:module
  via a postbuild step, so Node, Deno, and Bun load it as real ECMAScript
  Modules instead of the syntax-detection fallback (every relative import
  already carried a .js extension; the lone worker-thread require() is
  guarded). Bundler consumers are unaffected; CJS require consumers are
  unaffected.

Added

• Tree-shaking guard test + badges. A CI smoke test bundles a minimal
  import { flowChart } and asserts the recorder / detach / trace layers are
  pruned, plus true-ESM load of the main barrel and every subpath. README gains
  minzipped-size and tree-shakeable badges.