read the gamepad from dora-joy and publish twist and command

The pad moves to dora-joy, so this node keeps no hardware dependency and the
pad becomes reusable. It arrives on `joy` as a plain reading; `JoyInput.read`
treats silence past JOY_TTL_S as absence, because that node dying looks like
silence rather than like an unplugged pad and the arm cannot tell them apart.

Both control sources are now normalised to a [-1, 1] six-vector before anything
is scaled, and the scaling happens in one function. The web path used to pass a
velocity straight through without going near mapping, which is why the console
had to speak the arm's units. It no longer does.

`twist` (SI) and `command` (robot-agnostic verbs) are the standard ports. `jog`
and `request` still carry the same intent in dora-ulite6's units and service
names so the two repositories can move independently; LEGACY_REQUEST is the
only place that knows what that node calls a verb. Wire one or the other, never
both. `joint_jog` is specified in the manifest and deliberately not built.

Schemas are declared rather than inferred: pyarrow reads a null `value` as its
own type, so an inferred `command` would change its port's type between one
verb and the next.

Three bugs found while moving this code, each with a test:

- `Sample.active` compared raw axes against a threshold, but SDL rests a
  trigger at -1.0, so every connected pad read as in use for ever: the pad took
  the lease on plug-in and GAMEPAD_IDLE_RELEASE_S never fired.
- The e-stop latch was never consulted when deciding a velocity, so Back
  stopped the arm for one tick and the next stick nudge drove it again. Nothing
  on the pad could clear it either. It is now checked above the lease, and X
  releases it and clears the controller's error, as the console's RESET does.
- Buttons were read before the arbiter granted the lease, so the first press
  after the pad had been idle was swallowed: not owned yet when read, and no
  longer a rising edge by the next tick.

dora_teleop/ui.py

@@ -49,7 +49,10 @@ class Command:
     """One thing the console asked for."""
 
     type: str
-    velocity: list[float] = field(default_factory=list)
+    # Normalised, `[-1, 1]` per degree of freedom — a fraction of full speed,
+    # exactly what a stick reports. Not a velocity: the console does not know
+    # the robot's units and must not have to.
+    axes: list[float] = field(default_factory=list)
     action: str = ""
     preempt: bool = False
     enabled: bool = False
@@ -70,10 +73,10 @@ def command_of(payload: dict) -> Command | None:
         return None
 
     if kind == "jog":
-        velocity = payload.get("velocity") or []
-        if len(velocity) != 6 or not all(isinstance(v, (int, float)) for v in velocity):
+        axes = payload.get("axes") or []
+        if len(axes) != 6 or not all(isinstance(v, (int, float)) for v in axes):
             return None
-        return Command(type="jog", velocity=[float(v) for v in velocity])
+        return Command(type="jog", axes=[float(v) for v in axes])
     if kind in ("jog_stop", "estop", "reset", "home"):
         return Command(type=kind)
     if kind == "control":
@@ -83,7 +86,7 @@ def command_of(payload: dict) -> Command | None:
             preempt=bool(payload.get("preempt", False)),
         )
     if kind == "gripper":
-        return Command(type="gripper", enabled=bool(payload.get("vacuum", False)))
+        return Command(type="gripper", enabled=bool(payload.get("closed", False)))
     if kind == "freedrive":
         return Command(type="freedrive", enabled=bool(payload.get("enabled", False)))
     if kind == "move":
@@ -146,9 +149,10 @@ def arm_state(view: ArmView, jogging: bool) -> str:
 def snapshot(view: ArmView, owner: str | None, jogging: bool, timestamp: float) -> dict:
     """Build the telemetry object the console reads.
 
-    Every key here is read by name in `app.js`. `vacuum` is the console's name
-    for the mounted tool whatever it actually is, kept because renaming it would
-    mean editing the page for no gain.
+    Every key here is read by name in `app.js`, so this and the page change
+    together. The names are the robot-agnostic ones: `gripper` rather than
+    `vacuum`, because a page that says vacuum only fits a robot with one on it,
+    and `units` so a page can label a pose without guessing.
     """
     return {
         "type": "telemetry",
@@ -158,10 +162,14 @@ def snapshot(view: ArmView, owner: str | None, jogging: bool, timestamp: float)
         "arm_state": arm_state(view, jogging),
         "owner": owner or "none",
         "estop": view.estop,
-        "vacuum": view.tool_engaged,
+        "gripper": view.tool_engaged,
         "freedrive": view.freedrive_on,
         "position": dict(zip(POSE_KEYS, view.pose, strict=False)) if view.pose else None,
         "joints": list(view.joints),
+        # What `position` is in, so the page labels it rather than assuming. The
+        # telemetry ports carry whatever the robot publishes; only the command
+        # path is normalised.
+        "units": {"position": "mm", "rotation": "deg"},
     }