docs(6209): seventeen more test files — lesson shape and round trip, rule scope/moments/kind/surfacing, drift, deadlock race, backup, inception, backfill, claims, supersession, ledgers, family shapes

Docstrings and comments state the property and its reason in the present
tense. The session-context ledger test no longer describes the decision it
"used to pin"; the supersession tests state demote-not-filter without the
quote; one-row measurements become the general shape with their figures.

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

tests/test_family_shapes.py

@@ -1,10 +1,9 @@
-"""The shape ledger judging against family ideas, without a database
-(milestone 463 step 5).
+"""The shape ledger judging against family ideas, without a database.
 
 Pinned here: what a project's shapes say about an idea, when an answer
 contradicts them, which reference a shape in a given language is judged
-against, and the family arm's rule — measured on 2026-10-06 (#4991), and
-replayed below as the table it was chosen from. The two ledgers moving
+against, and the family arm's rule — measured, and replayed below as the
+table it was chosen from. The two ledgers moving
 together against Postgres are in tests/test_integration_family_adoption.py.
 """
 from __future__ import annotations
@@ -95,7 +94,7 @@ OWN, REF, OTHER = 1, 2, 3
 
 
 @pytest.mark.parametrize("name,hits,expected", [
-    # #4991's pairs, the reference as REF and the best other hit as OTHER.
+    # The measured pairs, the reference as REF and the best other hit as OTHER.
     ("A py->go", [(0.728, REF), (0.703, OTHER)], "family"),
     ("B py->go", [(0.715, REF), (0.675, OTHER)], "family"),
     ("D kt->kt", [(0.816, REF), (0.734, OTHER)], "family"),