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_note_usage.py

@@ -2,8 +2,8 @@
 
 Covers the payload shaping and the two contracts that make this safe to leave in
 the hot path: telemetry never raises, and telemetry never blocks. Plus the thing
-the feature exists for — that the write-path PLACE arm is now recorded, since
-before this it surfaced snippets while leaving no trace anywhere.
+the feature exists for — that the write-path PLACE arm is recorded, so a
+snippet it surfaces leaves a trace.
 """
 from unittest.mock import AsyncMock, MagicMock, patch