ci: ignore PERF401 (manual list comprehension) across the repo

[tonyandrewmeyer]

Disables PERF401, which suggests using a list comprehension rather than for loops. We still want to do this in many cases, but would prefer to decided on a case-by-case basis, rather than have it enforced as a rule.

Examples of where this is suggested (all for using list.extend and all in testing, but that's what we currently have as exceptions):

testing/src/scenario/_consistency_checker.py:556:17: PERF401 Use `list.extend` to create a transformed list
    |
554 |           for relation in _get_relations(endpoint):
555 |               if not isinstance(relation, PeerRelation):
556 | /                 errors.append(
557 | |                     f'endpoint {endpoint} is a peer relation; '
558 | |                     f'expecting relation to be of type PeerRelation, got {type(relation)}',
559 | |                 )
    | |_________________^ PERF401
560 |
561 |       known_endpoints = [a[0] for a in all_relations_meta]
    |
    = help: Replace for loop with list.extend

testing/src/scenario/_consistency_checker.py:564:13: PERF401 Use `list.extend` to create a transformed list
    |
562 |     for relation in state.relations:
563 |         if (ep := relation.endpoint) not in known_endpoints:
564 |             errors.append(f'relation endpoint {ep} is not declared in metadata.')
    |             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ PERF401
565 |
566 |     seen_ids: set[int] = set()
    |
    = help: Replace for loop with list.extend

testing/src/scenario/_consistency_checker.py:714:21: PERF401 Use `list.extend` to create a transformed list
    |
712 |               for attr in ('level', 'startup', 'threshold'):
713 |                   if getattr(check, attr) != getattr(plan_check, attr):
714 | /                     errors.append(
715 | |                         f'container {container.name!r} has a check {check.name!r} with a '
716 | |                         f'different {attr!r} ({getattr(check, attr)}) '
717 | |                         f'than the plan ({getattr(plan_check, attr)}).',
718 | |                     )
    | |_____________________^ PERF401
719 |
720 |       return Results(errors, [])
    |
    = help: Replace for loop with list.extend

[Copilot]

Pull request overview

This PR disables the PERF401 ruff rule, which flags manual list comprehension patterns and suggests using list.extend() or list comprehensions. The team prefers to handle these suggestions on a case-by-case basis rather than enforcing it as a blanket rule.

Key Changes

• Added PERF401 to the ignore list in the ruff configuration

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[benhoyt]

I agree, thanks. And I didn't see any existing uses using rg '\.extend\(' that we should undo.