Data streaming: stack test

This test aims to find issues with the work we have done towards the September 2026 Milestone so far.

We should do a full stack test of our software so far.

This should be conducted on the new streaming server or NDW1836 if unavailable along with the streaming control board and detector modules set up on EMMA (or another test instrument)

We should test:
`kdaectrl` begins a run -> streaming hardware streams udp as expected -> `event_udp_to_kafka` forms `ev44`/`pu00` correctly -> `kafka_event_aggregator` matches these up -> `kdaediag` reads them correctly.

Top-level workflow to test:
- A python command writes to a `begin` PV (and also a GUI if available). This does not have to be genie_python for this test - could manually use `p4p`.
- `kdaectrl` begins a run
- streaming hardware streams udp as expected
- `event_udp_to_kafka` forms `ev44`/`pu00` correctly
- `kafka_event_aggregator` matches these up and forwards to main `_events` stream
- `kdaediag` reads them correctly and forms correct diagnostics e.g. spectra

Other things to test:
- Pause/resume
- Runcontrol
- Hard/soft vetoes
- Multi-period run
- Timing modes
- Wiring and spectra mapping are correct

note that this does not need to follow any sort of deployment approach - if containers work for certain processes ie. redpanda and things that aren't IOCs that's great, but if we have to run things manually that's not the end of the world. Infrastructure/deployment work will decide on this stuff for production, this is just a test.

This will require input from DSG.

People to invite to see the test once it's working: HRPD scientists, SANDALS scientists (?), report outcome of test to MN/MG?