Yashima 0.4.0

What's Changed

• Added CompressedDataCodec, an explicit LZFSE-compressed Data codec for large text-like generated artifacts such as rendered HTML, JSON, manifests, and summaries.
• Kept compression opt-in: DataCodec remains uncompressed, and compressed entries use their own codec identity (compressed-data-lzfse-v1).
• Updated README installation guidance to the 0.4.x release line.
• Added test coverage for compressed data round-tripping, codec identity separation, and corrupted compressed payload handling.

Verification

• swift test passed with 99 tests.