fix the node manifest and make the example dataflow self-contained

Two problems, both found by the validate job once it could finally run.

categories named `teleop` and `input`, neither of which dora defines. The set is
fixed — sensor, actuator, robot, transform, filter, ml-inference, llm, speech,
communication, recorder, visualization, simulator, debug — and an unknown
variant makes the whole manifest unparseable, so every type annotation in it was
being ignored.

dataflow.yml spanned three repositories through sibling paths, which meant dora
could not resolve the other nodes' manifests and reported their typed outputs as
unannotated. It also could not be validated in CI, which clones one repo. The
house pattern is a self-contained dataflow, and this now follows it: teleop plus
a bench stand-in for the arm and the browser, both from this checkout. The real
three-node wiring moves to README.md, where a consumer would look for it.

The bench answers every service, publishes plausible telemetry, and prints the
velocities it is sent, so the node can be driven from a real gamepad with no
robot in the room. It is not a simulator and must not become one: it never
integrates a velocity or moves a pose.

AGENTS.md

@@ -77,6 +77,11 @@ a source goes away**.
   first time somebody picks up the pad. Errors name the variable.
 - **`dora_teleop/log.py`** — Timestamped stderr logging. stderr because dora reads a
   dynamic node's stdout.
+- **`examples/bench.py`** — A stand-in for the arm *and* the browser, so `dataflow.yml`
+  is self-contained and CI can validate it with no sibling clones. **It is not a
+  simulator** and must not become one: it never integrates a velocity or moves a pose. Its
+  job is to close the loop so this node can be watched, not to stand in for
+  `dora-ulite6` — anything needing the arm to actually respond needs the arm.
 - **`dora_teleop/probe.py`** — `dora-teleop-probe`: shows the raw axes, the buttons and the
   velocity that would be sent, with no dataflow and no arm. It exists because the indices
   in `mapping.py` are SDL's documented layout rather than an observed one, and a pad that