feat(vite): support node integration in renderers

[tzh476]

Closes #3961.

This follows up on #4258 and keeps its renderer-level nodeIntegration API. @rafael81 is retained as a co-author.

Why externalization is not enough

While validating #4258 in Electron, I found that externalizing Electron and Node.js built-ins leaves bare ESM imports in the renderer output. Vite loads that output as a browser module, which fails before application code runs:

Uncaught TypeError: Failed to resolve module specifier "electron".
Relative references must start with either "/", "./", or "../".

The development server similarly resolves Node.js modules to Vite browser-external stubs.

What changed

• add an opt-in renderer[].nodeIntegration setting
• load Electron and Node.js built-ins through runtime ESM shims in both serve and build modes
• support default, named, namespace, side-effect, and dynamic imports
• keep built-ins out of Vite dependency optimization and CommonJS conversion
• disable Rollup namespace freezing so CommonJS packages such as fs-extra can augment Node.js modules
• merge these settings with existing user Vite and Rollup configuration
• document the required Electron preferences and security implications

The runtime-shim approach follows the model proven by
vite-plugin-electron-renderer,
implemented here only for built-ins so Forge does not gain another runtime
dependency.

Security boundary

This option only configures Vite. The corresponding BrowserWindow must use nodeIntegration: true and contextIsolation: false. It should only load trusted local content; a preload script with contextBridge remains the safer default.

Validation

$ yarn vitest run --project fast packages/plugin/vite/spec
Test Files  4 passed (4)
Tests       19 passed (19)

$ yarn tsc -b packages/plugin/vite --force
# passed

$ yarn eslint packages/plugin/vite/spec/ViteConfig.spec.ts packages/plugin/vite/spec/config/vite.node-integration.config.spec.ts packages/plugin/vite/src/Config.ts packages/plugin/vite/src/config/vite.node-integration.config.ts packages/plugin/vite/src/config/vite.renderer.config.ts
# passed

$ yarn electron-markdownlint packages/plugin/vite/README.md
# passed

I also ran an Electron 39.2.6 / Vite 6.4.3 smoke fixture against the compiled Forge plugin in both development-server and production-build modes. It exercised default, named, namespace, side-effect, and dynamic built-in imports plus a transitive fs-extra CommonJS dependency; both modes delivered the expected IPC result.