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_services_retrieval_telemetry.py

@@ -929,10 +929,10 @@ async def test_a_section_is_complete_only_from_its_latest_contributor(
 def test_a_call_that_returned_nothing_still_records_what_it_nearly_showed():
     """The whole point, at the payload grain.
 
-    This is the row a threshold is tuned from and the one that used to carry no
-    score at all: `top_score` and `min_score` are both null here, correctly, and
-    a reader was left unable to tell a bar rejecting 0.71s from one rejecting
-    0.30s. Both render as a zero-result call.
+    This is the row a threshold is tuned from: `top_score` and `min_score` are
+    both null here, correctly, and without the near-miss a reader cannot tell a
+    bar rejecting 0.71s from one rejecting 0.30s. Both render as a zero-result
+    call.
     """
     p = _build_payload(
         user_id=1, source="pre_tool_rule", query="git push --force",