Expand ruff lint rule selection

[sgrava]

Summary

• Widen [tool.ruff.lint] select from E, F, I, Q to also include UP, B, SIM, with a documented ignore list for the rules left for separate discussion (including B905, zip() without strict=).
• Fix the resulting findings that were addressed: unused loop variables, a redundant isinstance check, dict.keys() iteration, and several pyupgrade/typing modernizations (Optional[X] -> X | None, typing.Callable -> collections.abc.Callable, etc).
• Drop mccabe.max-complexity and flake8-quotes.docstring-quotes — both configure rule sets (C90, and docstring quoting under D) that aren't in select, so they were dead config.

Rationale

#464 treats pyproject.toml's ruff config as the single source of truth for linting and is about to add the D (docstring) rule set on top of it. Before piling more rules onto that config, this PR turns on the other rule categories ruff already ships that we weren't using yet, fixes the findings that are genuine cleanups, and ignores the rest (including B905) for now — so the next docstring-focused PR lands on an intentionally-configured baseline instead of an implicit one.

[github-actions]

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