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>

.github/workflows/rustfs-pool-expand-test.yml

@@ -91,7 +91,7 @@ jobs:
 
       - name: Install RustFS package & start first pool
         run: |
-          ARGS=(--steps 1,2,3 -y --endpoint "${{ env.RUSTFS_API_ENDPOINT }}")
+          ARGS=(--steps "1,2,3" -y --endpoint "${{ env.RUSTFS_API_ENDPOINT }}")
           if [ -n "${{ inputs.package_url }}" ]; then
             ARGS+=(--package-url "${{ inputs.package_url }}")
           elif [ -n "${{ inputs.rustfs_version }}" ]; then
@@ -138,7 +138,7 @@ jobs:
           name: rustfs-pool-test-${{ github.run_id }}
           path: |
             /tmp/rustfs-pool-test.log
-            /tmp/rustfs-warp.log
+            /tmp/rustfs-warp.*.log
           if-no-files-found: warn
 
       - name: Reset test environment (after)