ref(⚡️): remove stylelint

[natemoo-re]

Another ref(⚡️) speedup—this time removing stylelint entirely

We've gone back and forth on having stylelint in the codebase. It was removed in June 2024 (biome added) and added back in November 2024 (biome removed). In the 68k+ commits between then and now, stylelint has detected zero meaningful violations.

• pre-commit runs stylelint with --quiet which suppresses warnings entirely
• stylelint CSS-in-JS support isn't great—the maintenance cost here has been us trying to get the two to play nicely
  • 12 stylelint-disable comments were all false-positives, not real issues
  • disabled rules in the config were all due to CSS-in-JS compat issues
• our custom @sentry/scraps lint rules enforce semantic token usage and general design system adherence across JS and CSS-in-JS which is a better enforcement mechanism

Results

Ran hyperfine against a few different configurations of pnpm lint to understand the performance win here.

Command	Mean	Range
pnpm run lint:css (stylelint only)	46.1s ± 0.2s	45.9s – 46.3s
pnpm run lint on master (eslint + stylelint)	144.8s ± 1.6s	143.7s – 146.0s
pnpm run lint on branch (eslint only)	92.4s ± 2.8s	90.4s – 94.4s

stylelint removal makes pnpm run lint 1.57x faster, saving ~52 seconds.

[github-actions]

🚨 Warning: This pull request contains Frontend and Backend changes!

It's discouraged to make changes to Sentry's Frontend and Backend in a single pull request. The Frontend and Backend are not atomically deployed. If the changes are interdependent of each other, they must be separated into two pull requests and be made forward or backwards compatible, such that the Backend or Frontend can be safely deployed independently.

Have questions? Please ask in the #discuss-dev-infra channel.