Read imports and exports for Python #40

Context

Hidden coupling (#17) and module depth (#18) read imports and exports through one adapter per language; only TypeScript/JavaScript has one.

Goal

Python repositories get Coupling.imports and Module.depth like TypeScript repositories do.

Acceptance criteria

• A Python adapter (a lightweight scanner, no new native dependency) resolves import x.y, from x import y, and relative imports (from . import y) to universe files, honoring src/ layouts and package roots from pyproject.toml; third-party imports are ignored.
• It lists a module's public names for depth: __all__ when present, otherwise top-level names without a leading underscore.
• A fixture repository with an imported pair, a hidden pair, a relative import, and an src/ layout proves both.

References

• Part of Read imports and exports beyond TypeScript and JavaScript #38. Builds on Flag hidden coupling: files that change together without importing each other #17 and Measure module depth as implementation size per exported symbol #18.