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_design_cascade.py

@@ -1,4 +1,4 @@
-"""The parent chain: walking it, and refusing to close it (milestone #254 step 1).
+"""The parent chain: walking it, and refusing to close it.
 
 Pure functions over a `{id: parent_id}` literal, so a whole hierarchy is one line
 of setup and no database is involved. That is the reason the cascade lives in its
@@ -99,7 +99,7 @@ def test_the_guard_survives_a_hierarchy_that_is_already_corrupt():
 
 # --- resolution -------------------------------------------------------------
 #
-# The cascade proper (milestone #254 step 2). Hierarchies are stated as literals
+# The cascade proper. Hierarchies are stated as literals
 # because resolve_tokens is pure and duck-typed — which is the whole reason it
 # lives here rather than inside the service.
 
@@ -384,7 +384,7 @@ def test_rows_without_a_supersedes_attribute_at_all_still_resolve():
 def test_rationale_cascades_like_purpose_and_is_a_different_question():
     """`purpose` is what the token is FOR; `rationale` is why it is this value.
     Rules carry the second routinely ("Success = Moss, aligned by design") and a
-    token row had nowhere to put it until now."""
+    token row needs a place to put it."""
     resolved = _by_name(resolve_tokens(
         APP, PARENTS,
         {