Remove __all__ declarations from src/utils modules

Start by opening each listed module: src/utils/conf_path.py, logging_levels.py, observability.py, safe_serialization.py, and trace_logging.py, and remove their all blocks. Then verify pyproject.toml [tool.mypy] and import conventions in these modules, especially where observability and conf_path re-export imported names. Run pytest tests/unit, mypy, pylint, and black --check as stated in acceptance. The issue is done when no all remains in those five files and all checks pass.

Description of Technical Debt

Five modules under src/utils/ end with an __all__ declaration:

__all__ controls exactly one thing: which names from module import * binds. There is no import * anywhere in src/ or tests/, and explicit imports are the convention the codebase already follows everywhere. The declarations therefore have no effect on any current call site.

Raised in review on PR #204 and agreed by both reviewer and author.

Impact of Technical Debt

• Maintenance with no return. Every new public name in these modules means editing a second list that nothing reads. The lists are in sync today, so the cost so far has been paid entirely in review attention rather than caught bugs.
• Misleading signal. A reader encountering __all__ reasonably infers that star imports are expected somewhere, or that the module has a curated public surface distinct from its non-underscore names. Neither is true.
• Inconsistent with the rest of the codebase. No other package in the project declares __all__, and it is not a pattern used in sibling Python projects, so it reads as local convention where there is none.

Category

Code Quality / Refactoring

Priority

Low - Nice to have

Proposed Solution

Delete the __all__ block from all five modules. Rely on the existing convention: a leading underscore marks a name private, everything else is importable.

Two things to confirm while doing it, both currently safe:

1. Re-exports. src/utils/observability.py lists TRACE_LEVEL and configured_log_level, which it imports from src/utils/logging_levels.py rather than defining; src/utils/conf_path.py similarly lists CONF_DIR and INVALID_CONF_ENV. Under mypy's no_implicit_reexport an imported name is only re-exported if it appears in __all__ or is aliased. The project's mypy config (pyproject.toml [tool.mypy]) does not enable strict or no_implicit_reexport, so removal changes nothing — but if that config is tightened later, importers of those names through observability would need to import them from logging_levels instead.
2. No star imports. grep -rn "import \*" --include=*.py src/ tests/ returns nothing. Re-run before merging in case one has been added.

Effort Estimate

< 1 hour

Dependencies / Related

• PR #204, where this was raised
• #193

Additional Context

Acceptance:

• No __all__ remains under src/.
• pytest tests/unit, mypy, pylint, and black --check all pass unchanged.
• No import statement anywhere needs editing, which is the point: if one does, that name was relying on a re-export and should be imported from its defining module.