feat(Android, FormSheet v5): Add onDetentChanged support

[t0maboro]

Description

This PR introduces support for the onDetentChanged event in the FormSheet. It reports the index of the newly settled detent.

Closes: https://github.com/software-mansion/react-native-screens-labs/issues/1561

Changes

• Android's BottomSheetBehavior operates on strict states, so the dynamic mapping in FormSheetBehaviorController safely translates these states into the corresponding detents array index depending on the current detent count configuration.
• Bound FormSheetDetentChangedEvent with JS

Before & after - visual documentation

detent-change.mov

Test plan

Marked SFT as applicable on Android.

Checklist

• Included code example that can be used to test this change.
• For visual changes, included screenshots / GIFs / recordings documenting the change.
• For API changes, updated relevant public types.
• Ensured that CI passes

[Copilot]

Pull request overview

This PR adds Android support for the FormSheet onDetentChanged event (already present on iOS), emitting the newly settled detent index to JS, and introduces a Single Feature Test (SFT) scenario to validate the behavior.

Changes:

• Android: wired a new FormSheetDetentChangedEvent through the host view manager/emitter chain and mapped BottomSheetBehavior state changes to detent indices.
• JS/Types: updated FormSheet prop docs to reflect cross-platform availability.
• Apps (SFT): added an onDetentChanged test scenario and made it available on both Android and iOS.

Reviewed changes

Copilot reviewed 10 out of 11 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/components/gamma/modals/form-sheet/FormSheet.types.ts	Removes the iOS-only platform annotation for onDetentChanged to reflect Android support.
apps/src/tests/single-feature-tests/form-sheet/test-form-sheet-on-detent-changed/scenario.md	Adds manual test instructions for verifying onDetentChanged.
apps/src/tests/single-feature-tests/form-sheet/test-form-sheet-on-detent-changed/scenario-description.ts	Registers the new SFT scenario metadata for Android + iOS.
apps/src/tests/single-feature-tests/form-sheet/test-form-sheet-on-detent-changed/index.tsx	Implements the test screen that displays the active detent index based on onDetentChanged.
apps/src/tests/single-feature-tests/form-sheet/index.ts	Exposes the new scenario from the form-sheet SFT index.
android/src/main/java/com/swmansion/rnscreens/gamma/modals/formsheet/FormSheetHostViewManager.kt	Exports the new direct event registration info for onDetentChanged.
android/src/main/java/com/swmansion/rnscreens/gamma/modals/formsheet/FormSheetHostEventEmitter.kt	Adds an emitter method to dispatch detent change events to JS.
android/src/main/java/com/swmansion/rnscreens/gamma/modals/formsheet/FormSheetHost.kt	Wires dialog detent changes to the React event emitter.
android/src/main/java/com/swmansion/rnscreens/gamma/modals/formsheet/FormSheetDialogManager.kt	Passes the detent change callback into the behavior controller and manages callback lifecycle.
android/src/main/java/com/swmansion/rnscreens/gamma/modals/formsheet/FormSheetDetentChangedEvent.kt	Introduces the Android event payload for detent index changes.
android/src/main/java/com/swmansion/rnscreens/gamma/modals/formsheet/FormSheetBehaviorController.kt	Listens to BottomSheet state changes and maps them to detent indices for event emission.

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