fix: make q_learning choose_action doctest deterministic

[ZainnQureshii]

Describe your change

The choose_action doctest in machine_learning/q_learning.py is flaky. It sets EPSILON = 0.0 inside the doctest, but doctest runs examples in a copy of the module globals, so choose_action() still reads the module's EPSILON = 0.2 and takes the random-exploration branch about one run in ten, printing 2 instead of 1.

Reproduced on master: repeated python3 -m doctest machine_learning/q_learning.py failed within the first 5 runs (Expected: 1, Got: 2). CI runs pytest with --iterations=8, so this hits PRs at random.

The fix patches random.random inside the doctest (return_value=0.99, so 0.99 < EPSILON is false and the greedy branch is always taken), the same unittest.mock.patch pattern used in other/fischer_yates_shuffle.py. Doctest-only change; the function body is untouched.

Verified: 200 consecutive python3 -m doctest machine_learning/q_learning.py runs pass, uvx pytest --doctest-modules machine_learning/q_learning.py passes, uvx ruff check and ruff format --check are clean.

• Add an algorithm?
• Fix a bug or typo in an existing algorithm?
• Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.
• Documentation change?

Checklist

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues, then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".

AI disclosure: prepared with AI assistance (Claude Code) and reviewed with GitHub Copilot, so I left the "all my own work" box unticked; nothing is copied from elsewhere.

🤖 Generated with Claude Code

[cclauss]

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