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_family_reach.py

@@ -1,7 +1,6 @@
-"""A family idea reaches every project on its platform, and no other
-(milestone 463 step 6).
+"""A family idea reaches every project on its platform, and no other.
 
-WHY THIS IS AN INTEGRATION TEST — the lesson-reach reasoning (#3730) holds
+WHY THIS IS AN INTEGRATION TEST — the lesson-reach reasoning holds
 here too: the reach is one `OR` inside the search's project filter, and only
 the ROWS that come back prove it. Every note embeds identically to the query,
 so scoping is the only thing that can separate them. The embedder is stubbed;