Third parity tier: @Bindable. Closes the two-way-binding hole for @Observable models — $model.property now projects a Binding into a reference type, so a bound control writes straight through to the model and its observation drives re-evaluation.

What's new

• @Bindable property wrapper (@dynamicMemberLookup) wrapping a reference; $model.property yields a Binding<Property> backed by a ReferenceWritableKeyPath (writes through the object without reassigning it).

Purely Swift-side sugar — no interpreter changes. Bound TextField/Toggle/Slider already accept a Binding, so a binding from $model.name is indistinguishable from one from @State.

Verification

• swift test — 2 new tests (projection + a TextField bound via $model.name writing back through the model), 41 total passing
• Emulator (new Bindable screen): typing the field, toggling, and dragging the slider all mutate one shared @Observable model, and the sibling Text views re-render from it