docs(6209): test prose in the present tense — "used to", "previously", "before this" restated as the failure shape

Twenty-eight test files described the code they guard by what it did
before a fix. Each is now the property and the failure it prevents, in the
present tense: the backfill snapshot, the per-dial calibration query, the
rule scope, the lesson trigger filter, the subshell global, the trash owner
scope, the version readout fallback, and others. A docstring line that
narrated the backup suite's own history is removed.

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

tests/test_integration_rule_scope.py

@@ -1,8 +1,8 @@
 """Real-Postgres tests for WHERE a rule reaches.
 
-A rule lives in a rulebook topic (global) or on one project. Retrieval used to
-ignore that and search every rule the user owned, so each project's rules were
-injected into every other project's sessions. What a mock cannot show is the
+A rule lives in a rulebook topic (global) or on one project. Retrieval that
+ignores the home and searches every rule the user owns injects each project's
+rules into every other project's sessions. What a mock cannot show is the
 join doing the scoping: these seed real rules with hand-made vectors and stub
 only the embedder, so every rule is an equally good match and the home alone
 decides what comes back.