chore: add script / CI job to validate light DOM styles in Lit components

[fbeaudoincoveo]

Task Description

We recently had a subtle regression that caused a production incident.

The root cause is that a component that got migrated from Stencil to Lit was in the Light DOM, but when the styles were migrated, a :host selector was used, causing the component's styles to leak onto its parent.

Let's add a script / CI job to automatically detect these patterns.

Acceptance Criteria

• Script has been created
• Script has been added to package.json
• CI job has been added to run after lint-check on each PR

Technical Notes

No response

Jira Ticket

No response

[fbeaudoincoveo]

Done in #6807