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_hook_pipefail_head.py

@@ -1,14 +1,14 @@
-"""Under `pipefail`, an early-exiting `head` must not void the output it kept (#4042).
+"""Under `pipefail`, an early-exiting `head` must not void the output it kept.
 
 The hooks run with `set -uo pipefail`. `hits=$(git grep -l … | head -4) ||
-hits=""` lost its four hits whenever git grep was still writing when head
-exited: SIGPIPE, a failed substitution, and the fallback wiped the result. It
-only showed on big outputs, so the by-name duplicate arm went silent for
+hits=""` loses its four hits whenever git grep is still writing when head
+exits: SIGPIPE, a failed substitution, and the fallback wipes the result. It
+only shows on big outputs, so the by-name duplicate arm goes silent for
 exactly the most-duplicated names.
 
 Two halves: the real function on a repo big enough to overflow the pipe, and
 the check_plugin pattern that keeps the shape out of every hook (shown able to
-fail, rule #167).
+fail).
 """
 from __future__ import annotations