Unconventional src.babel_validation import path makes the library hard to use standalone

[gaurav]

Problem

pyproject.toml installs the package as src so all imports read from src.babel_validation.X import Y. This means:

• If someone runs pip install babel-validation (or if this ever moves to a proper package), all import paths break.
• The import style is unusual — standard src-layout convention installs the package as babel_validation directly.

[tool.hatch.build.targets.wheel]
packages = ["src"]  # ← installs as src.babel_validation, not babel_validation

Suggested Fix

Change packages = ["src/babel_validation"] (or use package-dir to remap) and update all imports from from src.babel_validation.X import Y to from babel_validation.X import Y. This is a significant rename that touches every file in src/ and tests/.

Why it was deferred

Identified during PR #67 review. Changing the import style in that PR would have been too large a scope change. Keeping as a follow-up.