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_reply_discipline.py

@@ -70,8 +70,8 @@ def test_the_reply_carries_a_length_discipline():
 def test_the_reply_gets_a_second_pass_for_what_can_go():
     """Cutting is a separate act from writing, and needs saying separately.
 
-    The pre-existing check asked whether anything was MISSING, which a bloated
-    reply passes.
+    A check that asks only whether anything is MISSING is one a bloated reply
+    passes.
     """
     text = _flat()
     assert "what can go" in text