docs(6209): forty test files — design cascade and stylesheet, embeddings, family canon, forge, backup round trips, inception, placement, platforms, moments, rule move and verification, search scope, facets

Module and test docstrings state what is pinned without the record number
or step that introduced it. Incident accounts become the failure shape in
the present tense: the pipefail head, the code_shapes import, the export
order, the facet dialects, the cross-kind repeat, the write-once kind.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/test_integration_platforms.py

@@ -1,4 +1,4 @@
-"""Real-Postgres checks for platform membership (milestone 463 step 2).
+"""Real-Postgres checks for platform membership.
 
 The one invariant: detection only ever ADDS, and only where nobody has
 answered. A refresh that overwrote a "no" would put a project back into a