test(react-toast): add hook-level tests for toast components

[dmytrokirpa]

Summary

Adds hook-level tests for toast components.

Stacking Note

This PR is part of a stacked series and should be merged in order.

Merge order:

1. test(react-toast): add hook-level tests for toast components #36044 tests (this PR)
2. feat(react-toast): add base hooks/types and re-exports for headless composition #35914 base hooks/types and re-exports
3. feat(react-toast): headless toast implementation #36059 headless toast implementation

[github-actions]

📊 Bundle size report

✅ No changes found

[github-actions]

Pull request demo site: URL

[Copilot]

Pull request overview

Adds hook-level regression tests for useToast_unstable, useToastBody_unstable, and useToastTitle_unstable to lock down current behavior before the base-hook refactor in #35914 lands.

Changes:

• New unit tests for useToast_unstable covering components/slots, backgroundAppearance derivation from appearance prop, intent from context, and prop spreading.
• New unit tests for useToastBody_unstable covering slots, bodyId wiring, subtitle behavior, and backgroundAppearance from context.
• New unit tests for useToastTitle_unstable covering slots, titleId wiring, intent handling, default media icon injection per intent, and user override behavior.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
packages/react-components/react-toast/library/src/components/Toast/useToast.test.ts	Adds 8 hook tests for useToast_unstable.
packages/react-components/react-toast/library/src/components/ToastBody/useToastBody.test.ts	Adds 10 hook tests for useToastBody_unstable.
packages/react-components/react-toast/library/src/components/ToastTitle/useToastTitle.test.tsx	Adds 19 hook tests for useToastTitle_unstable, including default icon injection per intent.