Spotted during the live Playwright sweep: clicking Acknowledge or
Resolve updated the alert row but never fanned out a notification.
The handlers went straight to Store.Acknowledge/Resolve, bypassing
the hub.
Add Engine.Acknowledge and Engine.Resolve that wrap the store call
and dispatch the matching event to every enabled channel. The UI
handlers prefer the engine path when wired, and fall back to the
direct store call so unit tests that construct a Server without an
engine still work.
Use context.WithoutCancel for the goroutine dispatch — the request
context is cancelled the instant the handler returns 204, so the
naive 'go e.hub.Dispatch(ctx, ...)' was racing the response and
losing the channel-list query with 'context canceled'.
steve