fix: support Next.js 16.3.0

[Stanzilla]

Summary

• update the example and development dependencies from Next.js 16.3 preview to 16.3.0
• recover when Next.js returns a raw config module from its config cache
• keep one compiled React package instance during Vitest dependency pre-bundling
• cover the config-cache failure with a real repeated-load regression test

Root cause

The Rust React Compiler fallback loads next.config with rawConfig: true. Next.js 16.3.0 stores that raw module under the same cache key as a normal config load. A later Storybook project can receive the raw module without Next.js defaults. loadJsConfig then fails while it reads config.experimental.useTypeScriptCli.

The final release also gives the root package and example app separate Next.js peer snapshots. Vitest could pre-bundle two private compiled React copies, which caused invalid hook calls.

This change normalizes a cached raw config through the existing guarded fallback. It also aliases the private compiled React package directories so Vitest uses one instance.

Follow-up to #134.

Validation

• pnpm check
• pnpm build
• pnpm exec vitest run src/utils/next-config.integration.test.ts src/utils/next-config.test.ts src/index.test.ts src/plugins/next-swc/plugin.test.ts (9 tests)
• pnpm --dir example test:all --run (47 tests)
• NODE_OPTIONS=--unhandled-rejections=strict pnpm --dir example build-storybook

[Stanzilla]

should these be ^?

[ndelangen]

Closing in favor of the monorepo port: storybookjs/storybook#35882

This repository has moved into the Storybook monorepo — see #145.

[Stanzilla]

Oh neat, thanks