volt: Q139 -- the TOOLS.md drift guard is a fast leg, not a sweep-only cell

tools/tool_map.py

@@ -7,7 +7,8 @@ WHY THIS EXISTS
   queue block, in a reply -- and nothing states the whole set: which tool grades
   what, which flags each one actually accepts, which of them the two probe axes
   cover, and which leg of the operator's gate a failure shows up in. The closest
-  thing is `verify.py`'s `LEGS` table, which names ten of them.
+  thing is `verify.py`'s `LEGS` table, which names some of them and never all;
+  a leg count written here would be one more number to drift.
 
   A hand-written map would be a fourth notation of the defect this suite keeps
   grading: prose about the tree, one step from the thing it describes, with no