js: yarn v1 to pnpm (rollout stage 2 of 3, prod builds with pnpm)

[joshuarli]

stage 1: #91304

this is part 2 of a 3 stage rollout (we need to keep yarn around for prod cloudbuld which hits src/sentry/build/_static_assets.py):

1. (sentry) install pnpm, use it in dev+ci, keep prod build parts using yarn
2. (getsentry) same
3. (sentry) move prod build parts to pnpm
4. (getsentry) no action required since js-builder will have pnpm already
5. (sentry) delete yarn
6. (getsentry) same

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #92791      +/-   ##
==========================================
+ Coverage   87.90%   87.92%   +0.01%     
==========================================
  Files       10267    10266       -1     
  Lines      589971   589611     -360     
  Branches    22923    22841      -82     
==========================================
- Hits       518629   518425     -204     
+ Misses      70897    70740     -157     
- Partials      445      446       +1     

[joshuarli]

i'm going to force merge and fix-forward enforce-license-compliance.

it actually passed here: https://github.com/getsentry/sentry/actions/runs/15449512367

just did not generate a report because

 dependency-review
$GITHUB_STEP_SUMMARY upload aborted, supports content up to a size of 1024k, got 3321k. For more information see: https://docs.github.com/actions/using-workflows/workflow-commands-for-github-actions#adding-a-markdown-summary

edit: ok this is just a onetime thing / edge case, see actions/dependency-review-action#786