chore: enable the perflint and comprehension ruff rules

[cloudsmith-iduffy]

Description

Ruff can catch a handful of slow Python patterns for us, so this turns on two of its rule groups:

• perflint (PERF) — flags loop patterns that do more work than they need to, like building a list with .append() in a loop when a comprehension would do
• flake8-comprehensions (C4) — flags unnecessary or roundabout comprehensions, like wrapping something in a list comprehension that's already a list

Then it fixes everything they flagged: mostly table-building loops in the list, repos, dependencies and download commands rewritten as comprehensions, a couple of hand-rolled dicts replaced with dict.fromkeys() / a dict comprehension, and one comprehension that was a no-op deleted outright.

To be honest about the motivation: none of these rewrites make the CLI measurably faster today — they're microseconds on loops of ~30 rows, so there are no flame graphs or benchmarks here. The point is the guard. The credential helpers now run on every docker/npm request, and I'd rather have the linter shout before an accidentally slow loop lands in one of those paths than find it in a profile later. Both rules run in pre-commit and in CI via the existing ruff hook, so there's nothing new to set up.

One rule from the group is deliberately switched off: try/except inside a loop. All four places it flagged use the except as actual control flow — for example the credential chain trying each provider in turn and moving on when one fails. Restructuring those to save nanoseconds would make the code worse.

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update
• Refactoring
• Other (please describe)