build(deps-dev): upgrade to Vite 8 and @vitejs/plugin-react 6

[dcalhoun]

What?

Upgrade Vite from v7 to v8 and @vitejs/plugin-react from v5 to v6.

Supersedes #373 and #380.

Why?

Vite 8 replaces esbuild and Rollup with Rolldown and Oxc, the new Rust-based build toolchain. This keeps us on the latest major version and unblocks upgrading @vitejs/plugin-react to v6, which was required by the Dependabot PR.

How?

Dependency changes (package.json)

• vite: ^7.3.1 → ^8.0.0
• @vitejs/plugin-react: ^5.1.4 → ^6.0.1
• Removed vite-plugin-node-polyfills (does not support Vite 8, and was replaced by a lighter approach)

Replace vite-plugin-node-polyfills with resolve stubs (vite.config.js, src/stubs/node-modules.js)

PostCSS imports Node.js modules (path, fs, url, source-map-js) that don't exist in browsers. PostCSS marks these as false in its browser field, but @wordpress/block-editor imports PostCSS via direct file paths (e.g., postcss/lib/processor), bypassing that field and causing Vite to emit "Module has been externalized for browser compatibility" warnings.

The vite-plugin-node-polyfills plugin suppressed these by providing full browser polyfills (~600 KB in dependencies), but PostCSS never actually calls these modules at runtime—it guards usage behind Boolean() checks. A single empty stub module aliased via resolve.alias achieves the same result with zero bundle impact and no external dependencies.

Patch mousetrap global-bind plugin (patches/mousetrap+1.6.5.patch)

Vite 8's Rolldown bundler may reorder side-effect imports relative to value imports (rolldown/rolldown#6436, vitejs/vite#5142). This caused mousetrap's global-bind plugin to execute before the main mousetrap module, so window.Mousetrap was not yet set and bindGlobal was never added to the prototype—breaking @wordpress/keyboard-shortcuts.

The patch adds a require("mousetrap") fallback so the plugin resolves Mousetrap via the module system instead of relying on the global. This is preferred over Rolldown's output.strictExecutionOrder option, which would increase bundle size by injecting runtime helpers across the entire bundle.

Testing Instructions

1. Run the dev server (make dev-server) and verify the editor loads without errors in the browser console.
2. Run make build and verify it completes successfully.
3. Run make test-js and verify all tests pass.
4. Test with plugins that register keyboard shortcuts (e.g., Jetpack AI Assistant¹) and verify no mousetrap[bindGlobal] errors appear.

Accessibility Testing Instructions

N/A, no user-facing changes.

Footnotes

1. Requires adding a site to the demo app that has an active Jetpack connection—e.g., WoW/Atomic. ↩