Two real-run bugs found and fixed:
1. Phase 1 hardcoded patroni-1 as the expected standby_leader. The
bootstrap-race winner is actually nondeterministic (Patroni/etcd lock
race) — the original prod attempt had patroni-0 win it instead, which
the dry run never exercised. Fixed by polling BOTH patroni-0 and
patroni-1 each iteration and capturing whichever wins into
$LEADER_HOST, with the other becoming $REPLICA_HOST. Every later phase
(2,3,4,5,6,8,10) now references $LEADER_HOST/$REPLICA_HOST instead of
hardcoded hostnames.
2. Phase 1's wait window (240s) and Phase 2's (300s) were both far shorter
than the observed real basebackup duration for a ~42GB cluster
(8-11 minutes per prior dry-run/live polling). The role only flips to
standby_leader/replica AFTER the full copy completes, so both timeouts
could fire — and did — while a legitimate basebackup was still
in-progress, triggering a false-negative rollback. Both windows
extended to 1200s (20 min), with per-poll data-dir size logging
(timeout-guarded du -sh) so progress is observable instead of a silent
binary wait.