Adopt ruff 0.16 and its default rule set

[tony]

Summary

• Migrate the linter floor to ruff>=0.16.0 in the dev and lint dependency groups so contributors and CI see the same diagnostics
• Adopt ruff 0.16's curated default rule set by switching [tool.ruff.lint] select to extend-select, taking the enabled-rule count from 351 to 565

Changes

Dependencies

pyproject.toml: ruff floor raised to >=0.16.0 in the dev and lint groups. uv.lock: relocked, ruff 0.15.22 -> 0.16.0.

Lint configuration

select is now extend-select, with every entry on its own line carrying the name of the linter it selects. An explicit select replaces ruff's default rule set rather than extending it, so the project was silently opting out of the 413 rules ruff 0.16 recommends as its baseline. There is no DEFAULT token that a select list could name — leaving select unset is the only way to get defaults-plus-extras — so the file carries a comment saying so, to stop the key being reintroduced.

Findings fixed

PIE810 (multiple-starts-ends-with) in tests/test_install_widget.py: the docs-only package filter chained two startswith calls against the same name with or. str.startswith takes a tuple of prefixes, so this is one call.

Findings ignored

S102 (exec-builtin) in docs/conf.py: the Sphinx config reads the package's version metadata by exec'ing __about__.py, which keeps the docs build off an import of the package it documents. The input is a file in this repository, not user data, so the flake8-bandit warning has nothing to warn about. Scoped per-file, not globally.

Design decisions

Floor, not pin: >=0.16.0 rather than ==. The lockfile already reproduces the exact version for this repo; the floor exists to keep a contributor on an older ruff from producing a passing local run that fails CI.

extend-select, not wider prefixes: expanding the existing select to whole prefixes (PL, S, D, …) was measured elsewhere in this ecosystem and rejected — it is one to two orders of magnitude noisier than the curated default set, because it drags in every rule in each family rather than the subset ruff recommends.

One commit per decision: the config change, the fix, and the ignore each land alone, so the rationale for each rule is recoverable from git log rather than buried in a batch.

Test plan

• uv run ruff check . — clean
• uv run ruff format --check . — clean, now including Markdown code blocks
• uv run mypy — clean
• uv run py.test — full suite green, including doctests over src/, tests/, and docs/

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 88.98%. Comparing base (19a7bc1) to head (931f44e).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #356   +/-   ##
=======================================
  Coverage   88.98%   88.98%           
=======================================
  Files          12       12           
  Lines         690      690           
=======================================
  Hits          614      614           
  Misses         76       76           

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