Credibility pass: comments state constraints, not development history

A skeptical-cloner review flagged the patterns that read as AI-iteration
residue: test comments and section headers narrating the review process
that produced them, "legacy format" framing in a days-old repo, shadow
re-imports appended without reading file headers, one genuine machine
leftover (FIXTURE_CACHE = FIXTURE_CACHE), and a few register slips.
Every history-narrating comment is rewritten as the timeless invariant
it was guarding, test sections are grouped by behavior, function-local
imports are hoisted, and the README loses its one marketing clause and
heaviest dash runs. No behavior changes; 176 tests unchanged and green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/record_fixtures.py

@@ -18,8 +18,6 @@ from fixture_common import FIXTURE_CACHE
 from bggpipe.bgg_client import BGGClient
 from bggpipe.resolve import load_titles, resolve_entry
 
-FIXTURE_CACHE = FIXTURE_CACHE
-
 
 def main() -> None:
     if not os.environ.get("BGG_API_TOKEN"):