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_backfill_reads_current_text.py

@@ -1,4 +1,4 @@
-"""A backfill repairs to current truth; it does not replay a snapshot (#4262).
+"""A backfill repairs to current truth; it does not replay a snapshot.
 
 The bug these pin: every backfill used to SELECT the text alongside the id and
 then iterate that snapshot, sleeping between records. A run over a real corpus
@@ -90,8 +90,8 @@ async def test_a_record_deleted_between_the_scan_and_the_loop_is_skipped():
 
 @pytest.mark.asyncio
 async def test_a_record_whose_text_outran_its_vectors_is_re_embedded():
-    """The repair half (#4202 — a guard that refuses to write a bad value does
-    not undo the bad values already stored). Note 5 IS at the current version,
+    """The repair half: a guard that refuses to write a bad value does not
+    undo the bad values already stored. Note 5 IS at the current version,
     so the version comparison alone would skip it forever; its text is newer
     than its vectors, which is the only signal that separates "embedded from
     stale text" from "embedded correctly"."""
@@ -131,7 +131,7 @@ async def test_a_task_logged_since_its_vectors_is_re_embedded():
 
 @pytest.mark.asyncio
 async def test_a_corpus_that_is_genuinely_current_embeds_nothing():
-    """The guard must be able to stay quiet, or it is not a guard (#167) — and
+    """The guard must be able to stay quiet, or it is not a guard — and
     a backfill that re-embeds everything every boot is a different bug."""
     scan = _scan_session(all_ids=[1, 2, 3], current_ids=[1, 2, 3])