Fix test_idle_heartbeat: wait for shard connections and fix idle asse… #1603

Job	Run time
Build wheels / Build source distribution	11s
Build wheels / Prepare matrix to run for 3.13 on `linux,macos-x86,macos-arm,windows,linux-aarch64`	2s
Build wheels / Build wheels for macos-x86 on macos-15-intel	20m 24s
Build wheels / Build wheels for linux-aarch64 on ubuntu-24.04-arm	13m 30s
Build wheels / Build wheels for macos-arm on macos-14	10m 34s
Build wheels / Build wheels for windows on windows-2022	43m 59s
Build wheels / Build wheels for linux on ubuntu-24.04	14m 25s
Build wheels / upload_pypi	-1s
Publish wheels to PyPi	0s
	1h 43m 4s

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