- Updated io.Medium interface with Open() and Create() methods to support streaming.
- Migrated pkg/build, pkg/build/builders, and pkg/build/signing to use io.Medium.
- Added FS field to build.Config and updated build.Builder interface.
- Refactored checksum and archive logic to use io.Medium streaming.
- Updated pkg/release and pkg/build/buildcmd to use io.Local.
- Updated unit tests to match new signatures.