Consolidate test jobs into single serial job

Dan Notesteinrequested to merge
consolidate-test-jobs into main

Summary

Consolidate 6 parallel test jobs into 1 serial test job.

Tests are quick (~10s total), no need to spread across multiple runners.

Changes

  • .gitlab-ci.yml: 6 jobs → 1 job
  • CLAUDE.md: Updated pipeline docs

Test plan

  • Pipeline passes

Merge request reports