Release <ViewTransition /> to Canary (facebook#34712)

## Overview

This PR ships the View Transition APIs to `react@canary`:
- [`<ViewTransition
/>`](https://react.dev/reference/react/ViewTransition)
-
[`addTransitionType`](https://react.dev/reference/react/addTransitionType)

This means these APIs are ready for final feedback and prepare for
semver stable release.

## What this means

Shipping `<ViewTransition />` and `addTransitionType` to canary means
they have gone through extensive testing in production, we are confident
in the stability of the APIs, and we are preparing to release it in a
future semver stable version.

Libraries and frameworks following the [Canary
Workflow](https://react.dev/blog/2023/05/03/react-canaries) should begin
implementing and testing these features.

## Why we follow the Canary Workflow

To prepare for semver stable, libraries should test canary features like
`<ViewTransition />` with `react@canary` to confirm compatibility and
prepare for the next semver release in a myriad of environments and
configurations used throughout the React ecosystem. This provides
libraries with ample time to catch any issues we missed before slamming
them with problems in the wider semver release.

Since these features have already gone through extensive production
testing, and we are confident they are stable, frameworks following the
[Canary Workflow](https://react.dev/blog/2023/05/03/react-canaries) can
also begin adopting canary features like `<ViewTransition />`.

This adoption is similar to how different Browsers implement new
proposed browser features before they are added to the standard. If a
frameworks adopts a canary feature, they are committing to stability for
their users by ensuring any API changes before a semver stable release
are opaque and non-breaking to their users.

Apps not using a framework are also free to adopt canary features like
`<ViewTransition>` as long as they follow the [Canary
Workflow](https://react.dev/blog/2023/05/03/react-canaries), but we
generally recommend waiting for a semver stable release unless you have
the capacity to commit to following along with the canary changes and
debugging library compatibility issues.

Waiting for semver stable means you're able to benefit from libraries
testing and confirming support, and use semver as signal for which
version of a library you can use with support of the feature.

## Docs 

Check out the ["React Labs: View Transitions, Activity, and
more"](https://react.dev/blog/2025/04/23/react-labs-view-transitions-activity-and-more#view-transitions)
blog post, and [the new docs for `<ViewTransition
/>`](https://react.dev/reference/react/ViewTransition) and
[`addTransitionType`](https://react.dev/reference/react/addTransitionType)
for more info.

Author: eps1lon

fixtures/view-transition/src/components/App.js

@@ -3,7 +3,7 @@ import React, {
   useLayoutEffect,
   useEffect,
   useState,
-  unstable_addTransitionType as addTransitionType,
+  addTransitionType,
 } from 'react';
 
 import Chrome from './Chrome.js';

fixtures/view-transition/src/components/Page.js

@@ -1,6 +1,6 @@
 import React, {
-  unstable_addTransitionType as addTransitionType,
-  unstable_ViewTransition as ViewTransition,
+  addTransitionType,
+  ViewTransition,
   Activity,
   useLayoutEffect,
   useEffect,

packages/react-devtools-shared/src/__tests__/storeComponentFilters-test.js

@@ -251,7 +251,8 @@ describe('Store component filters', () => {
   });
 
   it('should filter ViewTransition', async () => {
-    const ViewTransition = React.unstable_ViewTransition;
+    const ViewTransition =
+      React.ViewTransition || React.unstable_ViewTransition;
 
     if (ViewTransition != null) {
       await actAsync(async () =>

packages/react-dom/src/__tests__/ReactDOMFizzViewTransition-test.js

@@ -40,7 +40,7 @@ describe('ReactDOMFizzViewTransition', () => {
     Stream = require('stream');
 
     Suspense = React.Suspense;
-    ViewTransition = React.unstable_ViewTransition;
+    ViewTransition = React.ViewTransition;
 
     // Test Environment
     const jsdom = new JSDOM(

packages/react-reconciler/src/__tests__/ReactErrorStacks-test.js

@@ -29,7 +29,7 @@ describe('ReactFragment', () => {
     React = require('react');
     Suspense = React.Suspense;
     Activity = React.Activity;
-    ViewTransition = React.unstable_ViewTransition;
+    ViewTransition = React.ViewTransition;
     ReactNoop = require('react-noop-renderer');
     const InternalTestUtils = require('internal-test-utils');
     waitForAll = InternalTestUtils.waitForAll;

packages/react-reconciler/src/__tests__/ReactLazy-test.internal.js

@@ -941,7 +941,7 @@ describe('ReactLazy', () => {
 
   // @gate enableViewTransition
   it('throws with a useful error when wrapping ViewTransition with lazy()', async () => {
-    const BadLazy = lazy(() => fakeImport(React.unstable_ViewTransition));
+    const BadLazy = lazy(() => fakeImport(React.ViewTransition));
 
     const root = ReactTestRenderer.create(
       <Suspense fallback={<Text text="Loading..." />}>
@@ -954,7 +954,7 @@ describe('ReactLazy', () => {
 
     await waitForAll(['Loading...']);
 
-    await resolveFakeImport(React.unstable_ViewTransition);
+    await resolveFakeImport(React.ViewTransition);
     root.update(
       <Suspense fallback={<Text text="Loading..." />}>
         <BadLazy />

packages/react-reconciler/src/__tests__/ViewTransitionReactServer-test.js

@@ -23,7 +23,7 @@ describe('ViewTransitionReactServer', () => {
     jest.resetModules();
     jest.mock('react', () => require('react/react.react-server'));
     ReactServer = require('react');
-    ViewTransition = ReactServer.unstable_ViewTransition;
+    ViewTransition = ReactServer.ViewTransition;
     ReactNoopFlightServer = require('react-noop-renderer/flight-server');
 
     jest.resetModules();

packages/react/index.development.js

@@ -45,6 +45,8 @@ export {
   startTransition,
   unstable_LegacyHidden,
   Activity,
+  ViewTransition,
+  addTransitionType,
   unstable_Scope,
   unstable_SuspenseList,
   unstable_TracingMarker,

packages/react/index.experimental.development.js

@@ -33,9 +33,9 @@ export {
   unstable_postpone,
   unstable_getCacheForType,
   unstable_SuspenseList,
-  unstable_ViewTransition,
+  ViewTransition,
   unstable_startGestureTransition,
-  unstable_addTransitionType,
+  addTransitionType,
   unstable_useCacheRefresh,
   useId,
   useCallback,

packages/react/index.experimental.js

@@ -34,9 +34,9 @@ export {
   unstable_postpone,
   unstable_getCacheForType,
   unstable_SuspenseList,
-  unstable_ViewTransition,
+  ViewTransition,
   unstable_startGestureTransition,
-  unstable_addTransitionType,
+  addTransitionType,
   unstable_useCacheRefresh,
   useId,
   useCallback,