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_retrieval_tuning.py

@@ -134,9 +134,8 @@ async def test_an_unknown_surface_is_refused_before_anything_is_written():
 @pytest.mark.asyncio
 @pytest.mark.parametrize("dial", ["threshold", "limit", "", "FLOOR"])
 async def test_an_unknown_dial_is_refused(dial):
-    """The near-misses are the old vocabulary — `threshold` and `limit` are what
-    these were called before this step, so they are exactly what a stale caller
-    will send, and a silent no-op there would be indistinguishable from a
+    """The near-misses are the generic vocabulary — `threshold` and `limit` are
+    what a caller that has not read the dial names will send, and a silent no-op there would be indistinguishable from a
     change that did not take."""
     session, ctx = _patches()
     with ctx[0], ctx[1], ctx[2], ctx[3], pytest.raises(ValueError):