refactor(project): update project to use rolldown over rollup

[joshblack]

Closes #6171

Update project to use rolldown over rollup. Rolldown is a part of voidzero and is powered by a Rust-based toolchain through projects like oxc. It features a rollup-compatible API so (ideally) speeds up our builds without many changes 😄

It also allows us to remove several rollup plugins that are baked into the library, namely ones for commonjs, json, resolution, and more. We can also remove some of our rollup custom plugins, like the one we have for preserving directives.

Changelog

New

Changed

• Update rollup-plugin-import-css to rolldown-plugin-import-css
  • Update how the plugin matches files by using rolldown's filter option which allows for more efficient bridging between Rust <-> JS
  • Update our logic for creating the *.module.css.js asset since rolldown's behavior is different than rollups. Now, the asset extension no longer gets a .js automatically so we needed to add that in and update the logic accordingly
  • Remove build step since Node.js natively supports *.ts extensions now 😄
• Update the following packages to use rolldown:
  • doc-gen
  • mcp
  • react
  • styled-react
• Add external deps to styled-react that were missing (clsx, deepmerge, and focus-visible)

Removed

Rollout strategy

• None; if selected, include a brief description as to why

This is a change to our internal build and should have no user-facing impact

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Latest commit: a548637

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[github-actions]

👋 Hi, this pull request contains changes to the source code that github/github-ui depends on. If you are GitHub staff, test these changes with github/github-ui using the integration workflow. Or, apply the integration-tests: skipped manually label to skip these checks.

[Copilot]

Pull request overview

This PR migrates the project from Rollup to Rolldown, a Rust-based bundler with a Rollup-compatible API. Rolldown is part of the voidzero toolchain powered by oxc (Rust) and offers performance improvements while maintaining compatibility with Rollup's API. The migration removes several rollup plugins that are now built into rolldown (commonjs, json, resolution) and simplifies the build configuration.

Key changes include:

• Migration of build configurations across 4 packages (react, styled-react, mcp, doc-gen) from Rollup to Rolldown
• Renaming and refactoring of the CSS import plugin from rollup-plugin-import-css to rolldown-plugin-import-css with updated filter-based API for efficient Rust/JS bridging
• Removal of custom "preserve-directives" plugin as rolldown has built-in support for directive preservation

Reviewed changes

Copilot reviewed 21 out of 24 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
packages/styled-react/script/build	Updated build command from rollup to rolldown
packages/styled-react/rollup.config.js	Deleted old rollup configuration
packages/styled-react/rolldown.config.js	New rolldown config with simplified plugin list (removed custom preserve-directives plugin)
packages/styled-react/package.json	Updated dependency from rollup to rolldown@^1.0.0-beta.52, added peer dependencies
packages/rollup-plugin-import-css/src/index.ts	Deleted old rollup plugin implementation
packages/rollup-plugin-import-css/rollup.config.js	Deleted old rollup build config for plugin
packages/rollup-plugin-import-css/package.json	Deleted old package.json for rollup plugin
packages/rolldown-plugin-import-css/tsconfig.json	New TypeScript config for rolldown plugin
packages/rolldown-plugin-import-css/tsconfig.build.json	New TypeScript build config for rolldown plugin
packages/rolldown-plugin-import-css/src/index.ts	New rolldown plugin using filter-based hooks for efficient JS/Rust bridging
packages/rolldown-plugin-import-css/package.json	New package.json with direct TypeScript exports (no build step needed)
packages/rolldown-plugin-import-css/README.md	Updated documentation to reference rolldown instead of rollup
packages/react/src/Text/Text.tsx	Refactored import to use direct path instead of barrel export (unrelated style change)
packages/react/script/build	Updated build command from rollup to rolldown
packages/react/rollup.config.mjs	Deleted old rollup configuration
packages/react/rolldown.config.mjs	New rolldown config with simplified plugins and dual build targets
packages/react/package.json	Updated dependency from rollup to rolldown@^1.0.0-beta.52, removed unused rollup plugins
packages/mcp/rolldown.config.js	Updated to import from rolldown, removed commonjs/json/node-resolve plugins
packages/mcp/package.json	Updated build commands and dependency from rollup to rolldown
packages/doc-gen/tsconfig.build.json	Added test exclusion to build config
packages/doc-gen/rolldown.config.js	Updated to use rolldown with platform: 'node', removed commonjs/json/node-resolve plugins
packages/doc-gen/package.json	Updated build commands and dependency from rollup to rolldown, reordered dependencies
package.json	Simplified workspaces glob pattern
package-lock.json	Updated lockfile with rolldown and related dependencies

Comments suppressed due to low confidence (3)

packages/doc-gen/rolldown.config.js:1

• The defineConfig import should be from 'rolldown' instead of 'rollup' to match the migration to rolldown. This config file is named rolldown.config.js but is still importing from the old 'rollup' package.
  packages/react/rolldown.config.mjs:4
• Unused import MagicString.

import MagicString from 'magic-string'

packages/styled-react/rolldown.config.js:5

• Unused import MagicString.

import MagicString from 'magic-string'

[primer-integration]

👋 Hi from github/github-ui! Your integration PR is ready: https://github.com/github/github-ui/pull/8202

[primer-integration]

🔴 ci completed with status failure.