basalt-26.3.2-rc-20260908: backup: TestBackupRestorePartitionedMergeDirectories failed

backup.TestBackupRestorePartitionedMergeDirectories [failed](https://mesolite.cluster.engflow.com/invocations/default/5d15a619-5664-4606-90d0-90e2519cd159?testReportRun=3&testReportShard=32&testReportAttempt=1#targets-Ly9wa2cvYmFja3VwOmJhY2t1cF90ZXN0) on basalt-26.3.2-rc-20260908 @ [807558e5e81666af257c811e925e4cae570abc28](https://github.com/cockroachdb/cockroach/commits/807558e5e81666af257c811e925e4cae570abc28):

```
=== RUN TestBackupRestorePartitionedMergeDirectories
test_log_scope.go:172: test logs captured to: outputs.zip/logTestBackupRestorePartitionedMergeDirectories1326503918
test_log_scope.go:82: use -show-logs to present logs inline
test_server_shim.go:168: automatically injected an external process virtual cluster under test; see comment at top of test_server_shim.go for details.
backup_test.go:1011: condition failed to evaluate within 2m0s: expected job status succeeded, but got running

goroutine dump: /mnt/engflow/worker/work/0/exec/bazel-out/k8-fastbuild/testlogs/pkg/backup/backup_test/shard_32_of_48_run_3_of_3/test.outputs/goroutine_dump_84925695.txt
testutils.go:385: no Invalid Descriptors
panic.go:694: -- test log scope end --
test logs left over in: outputs.zip/logTestBackupRestorePartitionedMergeDirectories1326503918
--- FAIL: TestBackupRestorePartitionedMergeDirectories (1175.63s)
```

Parameters:
- attempt=1
- race=true
- run=3
- shard=32
Help

See also: [How To Investigate a Go Test Failure \(internal\)](https://cockroachlabs.atlassian.net/l/c/HgfXfJgM)

Same failure on other branches

- #175010 basalt-26.3: backup: TestBackupRestorePartitionedMergeDirectories failed [A-disaster-recovery C-test-failure O-robot T-disaster-recovery branch-basalt-26.3 release-blocker]

/cc @cockroachlabs/disaster-recovery

[This test on roachdash](https://roachdash.crdb.dev/?filter=status:open%20t:.*TestBackupRestorePartitionedMergeDirectories.*&sort=title+created&display=lastcommented+project) | [Improve this report!](https://github.com/cockroachdb/cockroach/tree/master/pkg/cmd/bazci/githubpost/issues)

Start with TestBackupRestorePartitionedMergeDirectories in backup_test.go around line 1011, then rerun the targeted test with -show-logs. Inspect the captured test logs and goroutine dump, and compare the same failure in issue #175010; done means the job reaches succeeded and the test passes without the timeout.

Written by the indexing model from the issue text.