Add Python scaffold (uv project with pytest, mise toolchain)

python/README.md

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+# Show, Don't Tell — Python exercise workspace
+
+Python track for the "Show, Don't Tell — Using Examples with Coding Agents" exercise (Python 3.13 / uv / pytest).
+
+## Prerequisites
+
+- Python 3.13 and [uv](https://docs.astral.sh/uv/), versions pinned in `mise.toml`
+- If you use [mise](https://mise.jdx.dev): `mise install` installs both
+
+## Set up and run the tests
+
+```sh
+uv sync
+uv run pytest
+```
+
+## Layout
+
+| Directory | Contents |
+| --- | --- |
+| `src/order_domain`, `tests/order_tests` | Order domain with discount behaviour, and its tests (Round 1) |
+| `src/order_book_domain`, `tests/order_book_tests` | OrderBook state machine, and its integration tests (Round 2) |
+
+The exercise starts in its START state: all tests are green, the refactoring participants should do is NOT applied. The custom matcher example lives in `tests/order_tests` (`order_state.py`).

python/mise.toml

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+[tools]
+python = "3.13.16"
+uv = "0.12.21"

python/pyproject.toml

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+[project]
+name = "showdonttell"
+version = "0.1.0"
+requires-python = ">=3.13"
+
+[dependency-groups]
+dev = ["pytest>=8"]
+
+[tool.pytest.ini_options]
+pythonpath = ["src"]
+testpaths = ["tests"]