fix: scope hatch packages directive to wheel target only

CHANGELOG.md

@@ -16,6 +16,7 @@ All versions prior to 1.0.0 are untracked.
 - Standardized CLI flags to use hyphens (e.g., `--trust-config` instead of `--trust_config`). Underscore variants are still accepted for backwards compatibility via token normalization.
 
 ### Fixed
+- Fixed a bug where installing from the sdist produced an empty wheel with zero Python modules. The hatch `packages` directive was scoped to all build targets instead of the wheel target only, causing the sdist's flattened layout to not match the expected `src/` path. ([#636](https://github.com/sigstore/model-transparency/issues/636))
 - Fixed a bug where ignored symlinks could raise `ValueError`s if allow_symlinks was unset, even though they were skipped during serialization. ([#550](https://github.com/sigstore/model-transparency/pull/550))
 - Fixed a bug where any PEM encoded key could be read during the key-based flows which resulted in a Python exception because the rest of the code only supported elliptic curve keys. ([#573](https://github.com/sigstore/model-transparency/pull/573))
 

pyproject.toml

@@ -75,7 +75,7 @@ PyPI = "https://pypi.org/project/model-signing/"
 [tool.hatch.version]
 path = "src/model_signing/__init__.py"
 
-[tool.hatch.build]
+[tool.hatch.build.targets.wheel]
 packages = ["src/model_signing"]
 
 [tool.hatch.envs.hatch-test]