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_mcp_tool_search.py

@@ -168,8 +168,8 @@ async def test_fable_search_content_type_filters_at_service_layer():
 async def test_each_specific_kind_reaches_the_engine_filter_it_names(
     content_type, expected
 ):
-    """`note_type` and `task_kind` were parameters of the search all along —
-    what was missing was a way to ask for them from the agent's door. Asking
+    """`note_type` and `task_kind` are parameters of the search, and the
+    agent's door passes them through. Asking
     for a snippet must narrow to snippets, not merely to non-tasks."""
     _user_id_ctx.set(7)
     mock_search = AsyncMock(return_value=[])