fix gamepad layout and refuse a pad whose axes disagree

An Xbox One S pad over Bluetooth numbers its controls differently from the
indices this node shipped with: the right stick is on axes 2 and 3, the
triggers on 4 and 5, and the buttons carry gaps at 2 and 5. Against the old
layout an untouched pad reported a resting trigger as full right-stick
deflection, which asked for 30 deg/s of pitch while lying on the desk, held
the lease for ever so GAMEPAD_IDLE_RELEASE_S never fired, and moved a real
arm into a controller error. X toggled freedrive and LB was the E-STOP, so
the resulting latch could not be released from the pad at all.

Layout now carries the swept indices. Each pad is also measured the first
time it is seen at rest: a stick must rest near centre and a trigger near
the bottom of its travel, and a pad that does not fit reads as absent and is
named in the log rather than driving an arm from a numbering nobody checked.
The measured rest becomes each axis's zero, so a worn stick's tilt is
subtracted rather than deadzoned away and a trigger that reads 0 until it
first moves stops reading as half pressed.

Rest is never re-measured while the pad is in use, because doing that under
a held stick would record the deflection as centre and the arm would move
when the operator let go. The probe drives from the same calibration, so
what it prints is still what the arm would get, and it shows the mismatch.

Tests name their controls through axes_for and buttons_for instead of
numbering them; the positional lists are why a wrong index passed a green
suite.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tests/conftest.py

@@ -7,6 +7,7 @@ import pytest
 
 from dora_teleop.config import Config
 from dora_teleop.joy import Sample
+from dora_teleop.mapping import LAYOUT, TRIGGER_REST
 
 # The shape `dora-joy` publishes. Declared here rather than inferred for the same
 # reason it is declared there: pyarrow reads an empty `axes` list as `list<null>`,
@@ -66,13 +67,58 @@ def stick(axes=None, buttons=None, present=True):
     values = list(axes or [])
     values += [0.0] * (6 - len(values))
     # A trigger at rest reads -1, and a test that forgot to say so would look
-    # like both triggers held down.
-    for index in (2, 5):
+    # like both triggers held down. Which indices those are comes from the
+    # layout, so a test never has to be edited when a pad renumbers them.
+    for index in (LAYOUT.left_trigger, LAYOUT.right_trigger):
         if axes is None or index >= len(axes):
             values[index] = -1.0
     return Sample(axes=values, buttons=list(buttons or []), present=present)
 
 
+def axes_for(
+    left_x=0.0,
+    left_y=0.0,
+    right_x=0.0,
+    right_y=0.0,
+    left_trigger=TRIGGER_REST,
+    right_trigger=TRIGGER_REST,
+):
+    """Lay out a pad's axes by what each control is rather than by its index.
+
+    A test that numbers its axes says nothing about which control it meant, and
+    goes on passing while meaning something else once a pad renumbers them.
+    """
+    values = [0.0] * 6
+    values[LAYOUT.left_x] = left_x
+    values[LAYOUT.left_y] = left_y
+    values[LAYOUT.right_x] = right_x
+    values[LAYOUT.right_y] = right_y
+    values[LAYOUT.left_trigger] = left_trigger
+    values[LAYOUT.right_trigger] = right_trigger
+    return values
+
+
+def buttons_for(
+    grasp=False, release=False, clear=False, freedrive=False, yaw_left=False, yaw_right=False, estop=False
+):
+    """Lay out a pad's buttons by what each one does rather than by its index.
+
+    The same reason as :func:`axes_for`, and more pressing: an unpressed button
+    reads identically on every pad, so a test that numbers them is the only
+    place a wrong index could ever have been caught.
+    """
+    wanted = {
+        LAYOUT.grasp: grasp,
+        LAYOUT.release: release,
+        LAYOUT.clear: clear,
+        LAYOUT.freedrive: freedrive,
+        LAYOUT.yaw_left: yaw_left,
+        LAYOUT.yaw_right: yaw_right,
+        LAYOUT.estop: estop,
+    }
+    return [wanted.get(index, False) for index in range(max(wanted) + 1)]
+
+
 def joy_message(sample):
     """Build the Arrow row `dora-joy` would publish for one reading."""
     return pa.array(