Fully migrate pr-checks to ESM

[mbg]

The scripts in pr-checks are independent of the main codebase and are run in CI (or locally) using npx. All CI workflows that use scripts from pr-checks install Node24. We recently moved some of the scripts over to ESM, but kept CJS by default. This PR migrates the entire pr-checks project to ESM.

Risk assessment

For internal use only. Please select the risk level of this change:

• Low risk: Changes are fully under feature flags, or have been fully tested and validated in pre-production environments and are highly observable, or are documentation or test only.

Which use cases does this change impact?

Environments:

• Testing/None - This change does not impact any CodeQL workflows in production.

How did/will you validate this change?

• Unit tests - I am depending on unit test coverage (i.e. tests in .test.ts files).
• Other - The changed scripts only affect workflows, so if something does go wrong it will be easily visible.

If something goes wrong after this change is released, what are the mitigation and rollback strategies?

• Development/testing only - This change cannot cause any failures in production.

How will you know if something goes wrong after this change is released?

• Other - Workflow outcomes.

Are there any special considerations for merging or releasing this change?

• No special considerations - This change can be merged at any time.

Merge / deployment checklist

• Confirm this change is backwards compatible with existing workflows.
• Consider adding a changelog entry for this change.
• Confirm the readme and docs have been updated if necessary.

[Copilot]

Copilot review overview

🟢 Approval recommended

The migration consistently updates module configuration, entry-point detection, paths, dependencies, tests, and workflow references.

Review effort: Balanced
Findings: None

What changed in this PR

Migrates the independent pr-checks tooling from CommonJS to ESM while retaining tsx execution in CI and local development.

Changes:

• Enables ESM and Node.js 24 for pr-checks.
• Replaces CommonJS entry-point and directory detection.
• Renames remaining ESM-specific files to .ts and updates configuration and workflows.

File	Description
.github/​workflows/​pr-checks.yml	Uses the renamed changenotes script.
eslint.config.mjs	Removes obsolete .mts patterns.
package-lock.json	Locks updated Node.js type dependencies.
pr-checks/​.nvmrc	Selects Node.js 24.
pr-checks/​bundle-changelog.ts	Uses the ESM main-module check.
pr-checks/​bundle-metadata.ts	Uses the ESM main-module check.
pr-checks/​changelog/​validate.test.ts	Imports the renamed validator.
pr-checks/​changelog/​validate.ts	Converts the validator to TypeScript ESM.
pr-checks/​changenotes.ts	Updates validator imports and usage text.
pr-checks/​check-repo-size.ts	Uses the ESM main-module check.
pr-checks/​config.ts	Derives filesystem paths from import.meta.url.
pr-checks/​package.json	Enables ESM and Node.js 24 typings.
pr-checks/​prepare-changelog.ts	Uses the ESM main-module check.
pr-checks/​release-branches.ts	Uses the ESM main-module check.
pr-checks/​rollback-changelog.ts	Uses the ESM main-module check.
pr-checks/​sync-back.ts	Uses shared ESM-safe paths and entry detection.
pr-checks/​sync-checks.ts	Uses the ESM main-module check.
pr-checks/​sync.ts	Uses shared ESM-safe repository paths.
pr-checks/​tsconfig.json	Removes obsolete .mts inclusion.
pr-checks/​update-ghes-versions.ts	Uses the ESM main-module check.
pr-checks/​update-release-branch.ts	Uses the ESM main-module check.

---

💡 Add a code-review agent skill or configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

[mario-campos]

LGTM. Thanks!