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_integration_embedding_yields_to_delete.py

@@ -1,17 +1,17 @@
-"""#3262 against a real Postgres: the embedder loses the race, it doesn't run it.
+"""Against a real Postgres: the embedder loses the race, it doesn't run it.
 
-The reported failure was a deadlock — `DELETE FROM rulebooks` killed by the
-server while a detached `upsert_rule_embedding` held the other half of the
-cycle. It cannot be reproduced with mocks, because there is nothing to
+The failure is a deadlock — `DELETE FROM rulebooks` killed by the server
+while a detached `upsert_rule_embedding` holds the other half of the cycle.
+It cannot be reproduced with mocks, because there is nothing to
 deadlock: the whole bug lives in the ORDER two transactions take two row
 locks, which only a lock manager can adjudicate.
 
 So each test here holds a real delete open in one transaction and calls the
 embedder in another. What is being pinned is that the embedder RETURNS —
-promptly, having written nothing. Before the fix it would sit on the chunk
-rows waiting for a delete that is itself waiting on the insert's foreign key,
-and the test would hang rather than fail, which is why every call carries a
-deadline (rule 156).
+promptly, having written nothing. An embedder that sits on the chunk rows
+waiting for a delete that is itself waiting on the insert's foreign key would
+hang the test rather than fail it, which is why every call carries a
+deadline.
 """
 import asyncio
 from unittest.mock import AsyncMock, patch
@@ -53,8 +53,7 @@ SETTLE_DEADLINE_SECONDS = 30
 async def seeded():
     """A rule and a note to race against.
 
-    CLEANED AT SETUP, NOT TEARDOWN — the same constraint #3241 hit and the
-    reason this file exists. `create_rule` fires its own detached embedding
+    CLEANED AT SETUP, NOT TEARDOWN. `create_rule` fires its own detached embedding
     task; a teardown that deleted the rulebook would be racing exactly the
     thing under test, on a loop that is closing.
     """
@@ -141,7 +140,7 @@ async def test_a_rule_refresh_yields_to_a_delete_cascading_from_its_rulebook(see
 
 
 async def test_a_note_refresh_yields_to_a_delete_of_the_note(seeded):
-    """The note twin, which #3262 recorded as unverified. Notes are soft-deleted
+    """The note twin. Notes are soft-deleted
     day to day, so the hard delete a trash purge issues is the one that can put
     a lock on the row while a refresh is in flight."""
     async with async_session() as blocker: