b4e0d680f1
Ruff lint surfaced 23 violations across three rules; all addressed: UP017 (Use datetime.UTC alias): Replaced 13 sites of datetime.now(timezone.utc) with datetime.now(UTC), also adjusted from-imports accordingly. UTC is a Python 3.11+ alias for timezone.utc that ruff's pyupgrade rules prefer. UP042 (StrEnum): Replaced `class TagKind(str, Enum)` and `class SkipReason(str, Enum)` with `class Foo(StrEnum)`. StrEnum was added in Python 3.11 stdlib and is the modern idiom. Behavior is equivalent for our usage (the .value attribute, str(member) semantics). I001 (Import sorting): Added `known-first-party = ["backend"]` to ruff.toml's [lint.isort] so ruff groups `backend.*` imports correctly. Without it, ruff treated them as third-party and demanded a different grouping. The existing import order is stdlib → third-party → first-party → local relative, which ruff now accepts. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>