Pin Bun version to 1.2.22

Bun 1.2.23 introduced a regression causing false positives for nested
test() detection, breaking previously working tests with "test() inside
another test() is not yet implemented" errors.

Pinning to 1.2.22 until this regression is fixed.

https://github.com/oven-sh/bun/issues/5090



Co-Authored-By: Claude <noreply@anthropic.com>