v0.4.0-alpha of drip_flutter

Flutter render layer for DRIP — direct RenderObject binding with zero widget rebuilds. Changelog excerpt: ### Added - DripBuilder— general-purpose reactive builder widget. Accepts any DripReadable(DripState, DripComputed, or DripAsync) and rebuilds its subtree when the value changes. Scoped setState — only the builder's own subtree rebuilds. - DripSelect— multi-source reactive builder. Uses an internal DripComputedto combine multiple reactive sources. Rebuilds only when the combined output changes (version-clock and equality checked). Supports Dart 3 record types as combined value. - [...]