added ruff test

apps/autocal/README.md

@@ -112,6 +112,17 @@ calls them:
 
 - **Motion is refused** while the bus is not initialised, while the axis is
   unknown, or on a non-finite target — with a reason, never a silent no-op.
+- **A pose move is refused before the first axis moves** if any part of it is wrong:
+  a target past the P0 limit — millimetres for x/y/z, **degrees** for yaw/pitch, so a
+  400° stage turn cannot pass a 100 mm check — an axis mapping that is incomplete,
+  points outside the drive range, or claims one drive twice, or a rotary role on an
+  axis with no user-units-per-degree calibration. A sequence that stopped halfway
+  would leave the machine in a pose nobody simulated, so every check runs first.
+- **A move is stepped, not looped.** The drives are commanded one at a time from the
+  poll snapshots; a step that stalls (idle but short of its target), times out or
+  raises an alarm aborts the rest. That is also what makes **stop** work — it is an
+  ordinary command, so it runs at the next poll tick, and the queue is cancelled
+  before it is sent so no later axis is commanded.
 - **Homing needs a configured mode.** The vendor example pre-fills `17`, which
   is one specific drive's mode; AutoCal starts at `0` and refuses, so the
   operator chooses for the drive in front of them instead of inheriting a number