kmp-compose-slot-api

Replace data parameters with a `@Composable () -> Unit` slot parameter placed last so callers use trailing lambda syntax. The caller then decides what renders inside, whether text, icons, or loading spinners, without adding new component parameters.

Use slots when content is positional and belongs to a specific layout region of one component. Use CompositionLocal when a value like theme or a toast host must reach an arbitrary subtree many levels deep without threading parameters through every composable.

Use a scoped slot such as `@Composable RowScope.() -> Unit` when the caller needs layout scope features like `Modifier.weight()` inside the slotted content. Avoid scoped slots when the caller does not need layout scope, since they add noise without benefit.

Avoid slots when a simple value parameter suffices, such as a plain text label, when the parent must measure slot content before layout (use SubcomposeLayout), or when a component would need more than about four named slots, which signals it should be split.

Use compose test rules to set content with tagged slot lambdas, then assert the caller-provided content renders and callbacks fire. Also verify empty slot lambdas do not crash and capture Roborazzi screenshots for visual contract checks.