Remove orphaned programmatic fixtures

[GrahamCampbell]

Summary

• Remove programmatic fixture directories left orphaned after deleting CI-unreachable integration tests.
• Keep fixtures that are still referenced by unit tests or package integration tests.
• Reduce stale event-specific fixture code that no longer has a test entry point.

Tests

• npm run prettier-check
• npm run lint
• npm test -- -b
• npm run integration-test-run-package
• git diff --check