Brings the Go hub and web SPA work developed on feature/udpscope onto
main, without the udpscope client itself.
The trigger engine could not capture a sporadic event: it armed on the
live tail only, so a burst shorter than one push window was already past
by the time the FSM looked for it. It now searches the ring history for
the crossing, which also makes a capture reproducible from the same data
rather than dependent on push timing (wshub/trigger.go, ringbuf.go,
history.go).
Adds CSV/JSON export of the visible window (wshub/export.go) and reworks
the SPA: per-signal axis controls, a readable trigger panel, and a fix
for the flicker caused by repainting on every push instead of on a frame
tick (static/app.js, index.html, style.css).
BUFFER_AND_TRIGGER.md documents the ring/decimation/trigger interaction,
which is otherwise only inferable from the three files that implement it.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
