connectionEntry.send() is on the hot path: called once per connection
per broadcast tick. time.After allocates a timer that sits in the
runtime timer heap until it fires (50 ms), even when the channel send
succeeds immediately. At 1000 connected nodes, every tick leaks 1000
timers into the heap, creating continuous GC pressure.
Replace with time.NewTimer + defer timer.Stop() so the timer is
removed from the heap as soon as the fast-path send completes.
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