refactor: Bundle browser-test-runner

[mondoreale]

This pull request refactors the build and packaging process for the browser-test-runner package, introducing Rollup for bundling, improving module resolution, and updating various scripts and dependencies. The changes make the package outputs more consistent, enhance compatibility (especially for Electron and Karma), and modernize the codebase with ES module syntax and improved path handling.

Changes

Build & packaging improvements:

• Added a new rollup.config.mts configuration to bundle outputs for CommonJS, ES modules, Electron preload, and type declarations using Rollup.
• Updated package.json to define main, module, and types entry points, specify more granular files for publishing, and add build scripts (prebuild, postbuild, reset-self).
• Added new devDependencies for Rollup, plugins, and build tooling in package.json.
• Updated tsconfig.json to use "module": "preserve" and "moduleResolution": "bundler" for better compatibility with modern bundlers.

Code modernization & compatibility:

• Switched from CommonJS require to ES module import syntax in karma-setup.js for expect.
• Improved path resolution in createKarmaConfig.ts to use fileURLToPath and import.meta.url for locating setup and preload files, ensuring compatibility with ESM and Electron environments. [1] [2]
• Updated createWebpackConfig.ts to explicitly set timers: false in the fallback object for module resolution.

[Copilot]

Pull request overview

This pull request refactors the browser-test-runner package to introduce Rollup-based bundling, modernize the module system to ESM, and improve path resolution for better compatibility with Electron and Karma test environments.

• Introduced Rollup bundling to generate CommonJS, ES module, and Electron preload outputs
• Migrated from CommonJS require to ES module import syntax
• Updated path resolution to use fileURLToPath and import.meta.url for ESM compatibility

Reviewed changes

Copilot reviewed 6 out of 7 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
packages/browser-test-runner/tsconfig.json	Updated TypeScript compiler options to use module: "preserve" and moduleResolution: "bundler" for better bundler compatibility
packages/browser-test-runner/src/karma-setup.js	Changed from CommonJS require to ES module import for the expect library
packages/browser-test-runner/src/createWebpackConfig.ts	Explicitly set timers: false in webpack fallback configuration
packages/browser-test-runner/src/createKarmaConfig.ts	Updated path resolution to use fileURLToPath and import.meta.url for locating setup and preload files in ESM context
packages/browser-test-runner/rollup.config.mts	Added new Rollup configuration to bundle exports (CJS and ESM), preload file (CJS), karma-setup (ESM), and TypeScript declarations
packages/browser-test-runner/package.json	Updated entry points to use bundled outputs, added build scripts, and added Rollup-related devDependencies
package-lock.json	Updated lock file with new dependencies for Rollup, rimraf, tsx, and their transitive dependencies

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[Copilot]

Pull request overview

Copilot reviewed 8 out of 9 changed files in this pull request and generated 2 comments.

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[Copilot]

The files field specifies dist/karma-setup.js and dist/preload.cjs which are generated by the rollup bundler, but it doesn't include the sourcemap files that are generated alongside them. According to the rollup.config.mts, all bundled outputs have sourcemap: true, which means .map files will be generated. These sourcemap files should either be included in the published package (recommended for debugging) or explicitly excluded from the files array. Consider adding dist/karma-setup.js.map and dist/preload.cjs.map to the files array, or add !**/*.map to explicitly exclude them if they shouldn't be published.

Suggested change

	"dist/preload.cjs",
	"dist/karma-setup.js",
	"dist/preload.cjs",
	"dist/preload.cjs.map",
	"dist/karma-setup.js",
	"dist/karma-setup.js.map",