v1.2.0

Features

• Expose FileBlock as a public VM API via package:block/io.dart.
• Add FileBlock.open() and FileBlock.openRange() for lazy file-backed block views.
• Accept dart:io File directly in Block(List<Object> parts, ...) on IO platforms.

Behavior

• Make file-backed IO parts lazy to open while preserving reusable file-backed views.
• Make the default BlockBase.arrayBuffer() fallback materialize from stream() instead of requiring the reverse direction.

Documentation

• Add VM file-backed usage examples to the README.
• Document stream() as the preferred lazy integration path for downstream runtimes.