docs: explain what debug inspection is for

The dataflow turned on `enable_debug_inspection` without the README saying why
anyone would want it, which made it a line of configuration nobody could act on.

Documents the three commands it buys — topic list, topic echo, topic hz — and
that they need a coordinator rather than `dora run`. hz is the one that checks
the timings this node promises, so it names the measurement to expect.

README.md

@@ -201,6 +201,32 @@ is printed and forgotten. It closes the loop so this node's behaviour can be wat
 the lease changing hands, the deadman firing when you let go — not so the arm can be
 pretended at.
 
+### Watching the wire
+
+`dataflow.yml` sets `debug: enable_debug_inspection: true`, so dora will let you read what
+is actually on the wire without the bench printing anything. Run it under a coordinator
+rather than `dora run`:
+
+```bash
+dora up
+dora start dataflow.yml --uv --name teleop-bench
+```
+
+Then, in another terminal:
+
+```bash
+dora topic list -d teleop-bench                              # every edge in the graph
+dora topic echo -d teleop-bench teleop/jog                   # every velocity, live
+dora topic echo -d teleop-bench teleop/ui_state              # what the console would draw
+dora topic hz   -d teleop-bench teleop/jog --duration 10     # the re-send cadence
+```
+
+`hz` is the one that checks the timings this node promises. The `get_state` poll measures
+at 1.88 Hz against a configured `STATE_POLL_S` of 0.5, and with a pad held over the
+deadzone `teleop/jog` should sit near the 50 ms tick.
+
+Tear it down with `dora stop --name teleop-bench && dora down`.
+
 ## Development
 
 ```bash