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_create_tools_disambiguate.py

@@ -8,10 +8,10 @@ choice is the only moment a correction is cheap. The tool docstring IS the
 agent-facing contract (product guidance lives there and nowhere else), so a docstring that only documents parameters answers "how do I call
 this" while leaving "should I be calling this at all" unasked.
 
-The gap was lopsided before this: `create_rule` and `start_planning` both
-carried a real disambiguator, and `create_note` — far and away the
-highest-volume surface — carried none. Guidance sat in the rarest tool and
-was missing from the most common one.
+The gap tends to be lopsided: `create_rule` and `start_planning` are where a
+disambiguator gets written first, while `create_note` — far and away the
+highest-volume surface — is where it matters most. Guidance that sits only in
+the rarest tools misses the most common one.
 
 WHAT THIS PINS, AND WHAT IT DOES NOT