v1.58.0

Added

• Custom Button action handlers now receive a setVariable setter. CustomActionHandler args gained setVariable(name, { value, label?, kind? }), so a host-registered { type: "custom" } handler can write back into the ComposableScreen variable context — the imperative counterpart to the declarative { type: "setVariable" } action. Writes update both the render store (renderWhen / {{interpolation}}) and the branching store (resolveNextStepNumber), so a following "continue" branches on the new value. Backward compatible — existing handlers destructuring only { variables } are unaffected.

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