test(dns): stop the debounce burst test racing the scheduler - #1209
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The burst subtest fed ten events at a 10ms gap against a 60ms debounce window, which is only six times the margin. A loaded runner overshoots a 10ms sleep easily, and when one gap exceeded the window the debouncer settled mid-burst and emitted twice, failing on macOS CI while the same commit passed on a rerun. The gap narrows and the window widens, so a stall now has to exceed 400ms rather than 60ms to break it. The property under test is unchanged: events arriving closer together than the window still collapse into one emit.
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Closes #1208
The burst subtest fed ten events at a 10ms gap against a 60ms debounce window, which is only six times the margin. A loaded runner overshoots a 10ms sleep easily, and when one gap exceeded the window the debouncer settled mid-burst and emitted twice.
That is what happened on release PR #1207: the same commit failed on the push run and passed on the pull_request run, and the failure blocked a merge whose diff touched only the changelog, the README and the version string.
The gap narrows to 5ms and the window widens to 400ms, so a stall now has to exceed 400ms rather than 60ms to break it. The property under test is unchanged, events arriving closer together than the window still collapse into one emit, and the debouncer itself is untouched.
Verified by running the subtest 25 times while twelve concurrent copies of it competed for the CPU, which is the condition that produced the original failure.