Run ruff check in Lint, with F811 and F821 on for the package

[MaxGhenis]

Part of workstream W2 of the Autumn Budget CI plan, raised by the UK hub (notice 16).

Why

The Lint job runs only ruff format --check, so no lint rule runs in CI. Two open PRs, #2076 and #2354, each define Simulation.set_input. Git merges them cleanly and the second definition silently replaces the first. That's pyflakes F811 (redefinition of an unused name), and nothing catches it.

Change

In the Lint job of pr_code_changes.yaml (pull requests) and code_changes.yaml (main):

uvx ruff check .
uvx ruff check --select F811,F821 policyengine_uk

• First command: the rules pyproject.toml already selects, with its ignores. It passes on main today, so this adds no new failures.
• Second command: F811 (redefinition) and F821 (undefined name), which pyproject.toml ignores, on the package only. Neither has a finding there on main under ruff 0.15.7 (the uv.lock pin), 0.16.7 or 0.17.0 (what unpinned uvx resolves on CI now). The one F811 on main is in a docs notebook (docs/book/programs/gov/hmrc/income-tax.ipynb), which this leaves alone.
• The job name stays Lint. No branch rule requires any check today, so nothing changes there. It matters once Publish only the policyengine-uk release files whose checks passed #2306's merge queue and required checks arrive.

Checked

• Independent Opus 5.5 review: APPROVE. It also showed that a three-way merge of Lift the benefit cap only for the support component and the people HB reg 75F and UC reg 83 name, and cap only the family's benefits #2076 and Give a simulation its identifiers for a year before its data #2354's simulation.py gives F811 ... set_input from line 268 under this check.

• On main: both commands exit 0.

• A probe module with two def set_input in one class fails the second command: F811 Redefinition of unused set_input from line 2.

• actionlint, with shellcheck, is clean.

• Changelog fragment.

Interaction: #2306 (W2 release integrity) rewrites these workflow files and already carries this identical step in all three of them. If this lands first, #2306's rebase conflicts in each Lint hunk; take #2306's side. If #2306 lands first, close this PR.

Known limits

From the review:

• Docs and scripts. This workflow runs only when code, tests, .github, pyproject.toml or uv.lock change, but ruff check . and the existing ruff format --check . also cover notebooks under docs/ and scripts/. A docs-only PR can therefore land a violation that later code PRs trip over, as Suppress warnings in validation notebook (#587) #1696 did with formatting. Publish only the policyengine-uk release files whose checks passed #2306 fixes this by running Lint on every PR.
• Unpinned ruff. uvx ruff is unpinned, like the format step. Pinning it is a possible follow-up.
• What F811 misses. It catches a second definition only when the first was never used in between. Give a simulation its identifiers for a year before its data #2354's AST test for Simulation/Microsimulation is stricter for those two classes.

axiom: n/a: CI tooling

🤖 Generated with Claude Code

[MaxGhenis]

Hand-off to the UK hub from W2 of the Autumn Budget CI plan (session local_6c1ab389), per your notice 16.

• Head: 9228e14 on main c6d15c8.
• Review: an independent Opus 5.5 reviewer approved this head. It ran both commands under ruff 0.15.7, 0.16.7 and 0.17.0 (all exit 0), proved --select turns on rules the config ignores, and showed that the Lift the benefit cap only for the support component and the people HB reg 75F and UC reg 83 name, and cap only the family's benefits #2076 × Give a simulation its identifiers for a year before its data #2354 merge of simulation.py fails with F811 ... set_input from line 268. Its non-blocking points are in the PR body under "Known limits".
• CI: pending. Its full Test will fail only on main's test_dataframe_dataset.py::test_an_exported_frame_loads_back_and_exports_itself until that fix lands. Re-run after it does.
• Order: independent. Publish only the policyengine-uk release files whose checks passed #2306 carries the identical step. If this lands first, Publish only the policyengine-uk release files whose checks passed #2306 takes its own side in the Lint hunks when rebased; if Publish only the policyengine-uk release files whose checks passed #2306 lands first, close this.
• Follow-ups: Give a simulation its identifiers for a year before its data #2354's test_simulation_methods_defined_once.py docstring says "CI checks formatting only, so this test does"; that goes stale once this lands (Give a simulation its identifiers for a year before its data #2354's owner). Pinning ruff is an optional follow-up.