The test_idle_heartbeat test could fail with a KeyError when
shard-aware reconnection replaced connections during the sleep
interval. Skip connections not present in the original snapshot.

Also fix a trailing whitespace/dash in integration-tests.yml
that caused a YAML syntax issue in the paths-ignore list.

…rtion

Two issues caused this test to be flaky:

1. wait_for_all_pools only waits for the first connection per host.
   Shard-aware connections to remaining shards are opened asynchronously.
   When these complete during the test's sleep interval, they replace
   existing connections causing KeyError on the request_ids snapshot.
   Fix: add a helper that polls until all shard connections are
   established, called after connect().

2. execute_concurrent sent only len(hosts) queries, but with shard-aware
   routing each query hits one specific shard, leaving other shards'
   connections idle. The assertion that ALL connections are non-idle
   then fails.
   Fix: send more queries (2x num_connections) and relax assertion to
   check that at least some non-control connections became non-idle.