Add comprehensive ViewTransition component unit tests

[vansszh]

Summary

Add three new test files with comprehensive unit tests for the <ViewTransition> component, covering areas that currently lack test coverage.

The existing test coverage is minimal (6 tests in ReactDOMViewTransition-test.js, 4 in ReactDOMFizzViewTransition-test.js, 1 in ViewTransitionReactServer-test.js) relative to the 35KB+ of source code in ReactFiberCommitViewTransitions.js and ReactFiberViewTransitionComponent.js.

New Test Files

ReactDOMViewTransitionName-test.js (9 tests)

• Renders children without a wrapper element
• Uses explicit name prop when provided
• Generates auto name when name is not provided
• Generates auto name when name is 'auto'
• Preserves auto name across re-renders
• Supports multiple ViewTransitions as siblings
• Supports nested ViewTransitions
• Handles conditional rendering inside ViewTransition
• Handles ViewTransition mounting and unmounting

ReactDOMViewTransitionClass-test.js (14 tests)

• Accepts string as default/update/enter/exit/share class
• Accepts object with default key as class
• Accepts object with transition type keys
• Handles 'none' class which suppresses transition
• Handles 'none' in object class taking precedence
• Handles 'auto' class
• Combines multiple matching transition type classes
• Falls back to default when no transition types match
• Event class overrides default class
• Event class 'auto' nullifies the class
• Supports different classes for enter, exit, update, and share

ReactDOMViewTransitionWarnings-test.js (6 warning tests + 13 edge case tests)

• Warns when two ViewTransitions have the same name
• Does not warn for 'auto' name duplicates
• Does not warn for unnamed ViewTransitions
• Does not warn when duplicate is unmounted before new one mounts
• Only warns once per duplicate name
• Supports different unique names without warnings
• Handles rapid mount/unmount cycles
• Handles null/text/multiple DOM/Fragment children
• Handles list operations (add, remove, reorder)
• Handles Suspense fallback integration
• Handles key changes and name changes
• Handles deeply nested ViewTransitions
• Handles memo and forwardRef components

How did you test this change?

These are test-only additions. They follow the same patterns as the existing ReactDOMViewTransition-test.js test file (same mocking approach for document.startViewTransition, getBoundingClientRect, getAnimations, etc.).