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_projects.py

@@ -363,9 +363,9 @@ async def test_enter_project_fires_the_coverage_seed_on_the_owner(
 @pytest.mark.asyncio
 async def test_enter_project_hands_back_the_design_system_when_the_project_has_one():
     """The handshake is where an agent learns what binds it, and a design
-    system binds the same way a rule does. Before this it was reachable only by
-    an agent that already knew to call resolve_design_system — so the standards
-    were present in the store and absent from the work."""
+    system binds the same way a rule does. Reachable only by an agent that
+    already knows to call resolve_design_system, the standards would be present
+    in the store and absent from the work."""
     p = fake_project(id=5, design_system_id=9)
     design = {"id": 9, "title": "App kit", "guidance": [{"title": "House"}],
               "token_count": 95, "token_groups": ["surface"],