fix(kernel-ui): rationalize build externals and dependency declarations

[sirtimid]

Description

This PR rationalizes the build configuration and dependency declarations for the @metamask/kernel-ui package to make it a properly self-contained UI library.

Problem

The kernel-ui package had several configuration issues:

• Externalized dependencies that should be bundled for easier consumption
• Incorrectly declared peer dependencies
• Included unused dependencies (ses)
• TypeScript configs referenced packages that weren't actually used
• Type-only dependencies were in dependencies instead of devDependencies

Solution

Build Configuration Changes

• Bundle all dependencies except React: Changed from externalizing all MetaMask packages to bundling them, making kernel-ui truly self-contained
• Only externalize React ecosystem: Now only react, react-dom, and JSX runtimes are external
• Result: Bundle size increased from ~59KB to ~402KB, but consuming applications (like extension) now only need to provide React

Dependency Changes

• Removed unused dependencies:
  • ses - not imported anywhere in the source code
• Moved to devDependencies:
  • @metamask/ocap-kernel - only used for TypeScript type imports
• Peer dependencies:
  • Now only react and react-dom (removed @metamask/design-system-react - it's bundled)

TypeScript Configuration Cleanup

• Removed ses from types arrays in both tsconfig.json and tsconfig.build.json
• Removed references to unused packages (@metamask/streams, @metamask/kernel-shims)

Impact

✅ Simpler consumption: Applications using kernel-ui (like the extension popup) now only need to:

import '@metamask/kernel-ui/styles.css';
import { App } from '@metamask/kernel-ui';

✅ Better dependency management: Clear separation between what's bundled vs what consumers must provide

✅ Cleaner build: No warnings about missing dependencies, all depcheck issues resolved

Testing

• Build passes successfully for kernel-ui
• Extension builds and works with the updated kernel-ui
• No linter errors
• depcheck passes with no issues

---

Note

Kernel UI now bundles internal deps and only externals React (declared as peer), removes SES/types/references, and the extension build renames the _commonjsHelpers chunk.

• Kernel UI:
  • Build: Bundle previously externalized packages; only externalize react, react-dom, and JSX runtimes in packages/kernel-ui/vite.config.ts.
  • Dependencies: Move react and react-dom to peerDependencies; remove react, react-dom, and ses from dependencies in packages/kernel-ui/package.json.
  • TypeScript: Remove ses from types arrays; drop unused references to @metamask/kernel-shims and @metamask/streams in tsconfig.json/tsconfig.build.json.
• Extension:
  • Build: Customize chunkFileNames in packages/extension/vite.config.ts to rename _commonjsHelpers to commonjsHelpers.js.

^{Written by Cursor Bugbot for commit 85e7deb. This will update automatically on new commits. Configure here.}

[rekmarks]

LGTM!