fix: replace dist/ with src/ in test imports (#71)

[michaeldistel]

Closes #71

Summary

• 8 test files imported from dist/ causing tests to silently validate stale compiled output instead of current source
• Replace dist/ with src/ in all import paths; Vitest's Vite pipeline transpiles .ts on-the-fly so dist/ is never needed
• cli-library.test.ts left unchanged — it invokes dist/cli.js as a subprocess which correctly requires a built binary

Testing

npm test: 51 test files passed, 1414 tests passed, 7 skipped — no regressions