test(pool): cover rebalance retry and cold-start recovery (#6720)

* test(pool): fix warp log path and retry rebalance start

- warp writes now use a unique mktemp log file instead of a fixed
  /tmp/rustfs-warp.log: the runner user could not write the stale
  root-owned file, which made the background warp process die instantly
  (warp never ran). The workflow uploads /tmp/rustfs-warp.*.log.
- rebalance start is retried (6x, 20s apart): nightly builds gate
  rebalance activation on a live cross-pool fence fleet capability proof
  that takes ~10-20s to re-establish after a pool joins. Verified live:
  attempt 1 fails with 500 'pool activation requires a live fleet
  capability proof', attempt 2 succeeds.

* test(pool): annotate known server-side issues in failure output

When a node fails to start, grab the rustfs journal tail and match known
server-side error signatures (e.g. the fleet capability proof cold-start
regression, rustfs/backlog#2031), printing a hint with the tracking issue.
Also annotate the rebalance-start retry exhaustion and the rc.3 decommission
metacache-listing failure with actionable guidance.

* fix(ecstore): defer rebalance activation without fleet proof

---------

Co-authored-by: 马登山 <cxymds@qq.com>
Co-authored-by: cxymds <cxymds@gmail.com>

crates/ecstore/src/services/rebalance/mod.rs

@@ -49,8 +49,8 @@ mod worker;
 
 #[cfg(feature = "test-util")]
 pub use entry::test_util::PausedRebalanceEntryTestFixture;
-pub(crate) use meta::is_rebalance_conflicting_with_decommission;
 pub use meta::{decode_rebalance_stop_propagation_record, encode_rebalance_stop_propagation_record};
+pub(crate) use meta::{is_rebalance_conflicting_with_decommission, rebalance_requires_worker_activation};
 pub use types::{
     DiskStat, RebalSaveOpt, RebalStatus, RebalanceCleanupWarningEntry, RebalanceCleanupWarnings, RebalanceInfo, RebalanceMeta,
     RebalanceStats, RebalanceStopPropagationRecord,