pyproject.toml: non-idiomatic src.<pkg> import path for downstream consumers

[gaurav]

Background

pyproject.toml currently sets:

[tool.hatch.build.targets.wheel]
packages = ["src"]

This exposes the package as src.babel_validation rather than the idiomatic babel_validation. Downstream consumers must write from src.babel_validation.X import Y, which is unusual and may surprise users expecting standard package layout.

Standard layout alternative

[tool.hatch.build.targets.wheel]
packages = ["src/babel_validation"]

This would expose babel_validation directly. All internal imports (from src.babel_validation...) would also need to change to (from babel_validation...).

Notes

• The current choice appears intentional (there is a comment in pyproject.toml). This issue is just documenting the trade-off flagged during the Opus code review of PR Add GitHub-issue-driven test framework (+ src/ library carve-out) #67.
• Any change here requires updating all from src.babel_validation... imports throughout the test suite and library.
• Not blocking; assess whether downstream consumer ergonomics matter before changing.