pkg/sql/copy/copy_test: TestLargeDynamicRows failed

pkg/sql/copy/copy_test.TestLargeDynamicRows [failed](https://mesolite.cluster.engflow.com/invocations/default/863f67a0-0e24-4659-acbb-8bdb619b0c10?testReportRun=3&testReportShard=1&testReportAttempt=1#targets-Ly9wa2cvc3FsL2NvcHk6Y29weV90ZXN0) on release-25.4.17-rc @ [0447ee0a79bd81f5bcb15bcd613e6653dd0d1e0f](https://github.com/cockroachdb/cockroach/commits/0447ee0a79bd81f5bcb15bcd613e6653dd0d1e0f):

```
=== RUN TestLargeDynamicRows
test_log_scope.go:171: test logs captured to: outputs.zip/logTestLargeDynamicRows4161641603
test_log_scope.go:82: use -show-logs to present logs inline
test_server_shim.go:154: automatically injected a shared process virtual cluster under test; see comment at top of test_server_shim.go for details.
copy_test.go:626:
Error Trace: pkg/sql/copy/copy_test.go:626
Error: Received unexpected error:
ERROR: duplicate span 288481614935657682 (SQLSTATE XXUUU)
Test: TestLargeDynamicRows
panic.go:635: -- test log scope end --
test logs left over in: outputs.zip/logTestLargeDynamicRows4161641603
--- FAIL: TestLargeDynamicRows (22.54s)
```

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

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

/cc @cockroachlabs/sql-foundations

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Start with pkg/sql/copy/copy_test.go at TestLargeDynamicRows and the failure logs linked in the issue; rerun the test with the reported race configuration to determine whether the duplicate span error reproduces. Done means the test completes without the unexpected duplicate-span error under the relevant configuration.

Written by the indexing model from the issue text.