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_write_path_trigger.py

@@ -1342,10 +1342,10 @@ async def test_a_pulled_snippet_already_seen_is_evidence_not_menu():
     # ...and the menu carries it, marked.
     seven = next(line for line in out["context"].splitlines() if "#7" in line)
     assert "seen" in seven
-    # #8 (0.80) now falls OUTSIDE the margin band, because #7 (0.91) anchors it
+    # #8 (0.80) falls OUTSIDE the margin band, because #7 (0.91) anchors it
     # at 0.81 instead of being filtered out first. That is the point rather than
     # a casualty: the band measures distance from the best answer, and the best
-    # answer here is #7 — suppressing it used to promote a materially weaker hit
+    # answer here is #7 — suppressing it would promote a materially weaker hit
     # into a slot it had not earned, with nothing in the output saying so.
     assert out["note_ids"] == [7]
     # The stamp saw the pull and the resemblance score for this payload.