v1.0.0

Initial release.

• SmallJsonInterceptor for Dio: advertises support via X-Small-Json, decodes application/vnd.smalljson+json responses in place (including error responses), rewrites the content type back to application/json, and surfaces corrupt envelopes as DioExceptions.
• SmallJsonCodec implementing SmallJson wire format v1: packed mode everywhere, deflate mode on dart:io platforms (web advertises packed-only automatically).
• Strict envelope validation with typed exceptions.
• Cross-implementation test vectors shared with the nylo/smalljson Laravel package, verified in both directions.