Add show_round, ask_choice and play_game with injectable input and
output, and make python -m higher_lower play a game. Each account is
shown once per game; a wrong guess or running out of accounts ends it.
Invalid input is re-asked. Ctrl+C and Ctrl+D leave with a goodbye.
Cover the loop with scripted tests (36 passing).
Task: MIL-003#1
Task: MIL-003#2
Task: MIL-003#3
Task: MIL-003#4
Task: MIL-003#5
Closes#12Closes#13Closes#14Closes#15Closes#16
Add pyproject.toml (Python >=3.13, no runtime dependencies, pytest as a
dev extra), the src/higher_lower package with an empty constants module
and an entry-point stub, a smoke test, and the Doxyfile for the Doxygen
comments in the source. Ignore the Doxygen output in .gitignore.
Verified in a fresh .venv: pip install -e ".[dev]", pytest (2 passed),
python -m higher_lower and doxygen Doxyfile without warnings.
Task: MIL-001#1
Task: MIL-001#2
Task: MIL-001#3
Task: MIL-001#4
Closes#1Closes#2Closes#3Closes#4