Fix pytest imports and document local/VS Code test workflow

[IliTheButterfly]

Motivation

• Tests were failing to import package modules because they referenced src.eb_macro_gen instead of the installed package namespace, causing pytest collection errors.
• Developers need clear instructions to run tests locally and from VS Code with the repository src/ layout.

Description

• Updated tests to import from the package namespace (eb_macro_gen) instead of src.eb_macro_gen so imports work when running tests from the repo root.
• Added pytest configuration in pyproject.toml with pythonpath = ["src"] and testpaths = ["tests"] to ensure consistent discovery with the src/ layout.
• Added a .vscode/settings.json file that configures VS Code testing to use pytest, sets the test args to tests, sets the workspace cwd, and adds ${workspaceFolder}/src to python.analysis.extraPaths for editor resolution.
• Added a Running tests section to ReadMe.md describing how to run tests via the CLI and how to use the preconfigured VS Code testing setup.

Testing

• Ran pytest -q after the changes and all tests passed: 18 passed in 0.27s.

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Codex Task