Handle Rollup FATAL events in watch mode

[2ws2khc2zh-rgb]

Summary

• Treat Rollup FATAL watch events the same as ERROR events.
• Extract the watch error-event check into a small helper for focused coverage.
• Add a unit test covering ERROR, FATAL, and a non-error watch event.

Validation

• yarn test could not be run locally because this environment does not have Node.js/Yarn installed.

Closes #184

[vercel]

@2ws2khc2zh-rgb is attempting to deploy a commit to the EGOIST's projects Team on Vercel.

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[2ws2khc2zh-rgb]

The Vercel preview deployment is blocked on team authorization for the EGOIST project, which only a project/team member can approve. No contributor-side action is available from this fork.

The source change is limited to Rollup watch event handling, and the configured Socket checks are passing.