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_rule_surfacing.py

@@ -10,12 +10,9 @@ planning read carries — and what mocks can't prove about it:
    comparison, never a similarity score.
 2. An UNTAGGED global rule is not listed: it applies everywhere and arrives by
    retrieval, and listing every one under every project would say nothing.
-3. A `co_surfaces` partner arrives with its other half — the failure that made
-   merging rule 144 into rule 46 look like the only fix — unless the partner
-   lives on a different project, because an edge is not a way in.
-
-Milestone 414 dropped the suppression claim ("an explicit suppression outranks
-an edge") with suppressions themselves.
+3. A `co_surfaces` partner arrives with its other half — without it, merging
+   two rules that must arrive together looks like the only fix — unless the
+   partner lives on a different project, because an edge is not a way in.
 """
 import pytest
 import pytest_asyncio
@@ -102,9 +99,9 @@ async def test_a_tagged_global_rule_is_listed_for_a_project_that_works_in_its_ar
 
 @pytest.mark.integration
 async def test_co_surfaces_drags_in_the_half_that_would_have_been_missed(world):
-    """Rule 144 was split off rule 46 and folded back the same day because
-    "either rule could surface without the other". This is the edge that makes
-    that unnecessary: the partner arrives even though nothing else selected
+    """Two rules that must arrive together get folded into one because either
+    could surface without the other. This is the edge that makes that
+    unnecessary: the partner arrives even though nothing else selected
     it, and says why it is here."""
     partner = await rulebooks_svc.create_rule(
         world["topic"], world["owner"], "Version names are labels",