basalt-26.3.2-rc-20260908: sqlproxy: TestPrivateEndpointsACL failed

sqlproxy.TestPrivateEndpointsACL [failed](https://mesolite.cluster.engflow.com/invocations/default/f0916551-4348-4015-a964-7d1ed87aeec5?testReportRun=1&testReportShard=7&testReportAttempt=1#targets-Ly9wa2cvc3FscHJveHk6c3FscHJveHlfdGVzdA==) on basalt-26.3.2-rc-20260908 @ [807558e5e81666af257c811e925e4cae570abc28](https://github.com/cockroachdb/cockroach/commits/807558e5e81666af257c811e925e4cae570abc28):

```
=== RUN TestPrivateEndpointsACL
test_log_scope.go:172: test logs captured to: outputs.zip/logTestPrivateEndpointsACL3684763538
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.
test_server_shim.go:639: DRPC is enabled (via testserver factory defaults)
proxy_handler_test.go:489: -- test log scope end --
test logs left over in: outputs.zip/logTestPrivateEndpointsACL3684763538
--- FAIL: TestPrivateEndpointsACL (19.99s)
=== RUN TestPrivateEndpointsACL/private_connection_allowed
proxy_handler_test.go:418:
Error Trace: pkg/sqlproxy/proxy_handler_test.go:2987
Error: Received unexpected error:
failed to connect to ``user=bob database=my-tenant-10.defaultdb``: 127.0.0.1:44707 (127.0.0.1): failed SASL auth: timeout: write tcp 127.0.0.1:41408->127.0.0.1:44707: i/o timeout
Test: TestPrivateEndpointsACL/private_connection_allowed
--- FAIL: TestPrivateEndpointsACL/private_connection_allowed (3.09s)
```

Parameters:
- attempt=1
- race=true
- run=1
- shard=7
Help

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

Same failure on other branches

- #174456 sqlproxy: TestPrivateEndpointsACL failed [C-test-failure O-robot T-cloud-platform branch-master]

/cc @cockroachlabs/sqlproxy-prs

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Start with `pkg/sqlproxy/proxy_handler_test.go`, especially `TestPrivateEndpointsACL` and its `private_connection_allowed` case around line 418; inspect the linked test failure report and logs for the SASL auth timeout. Compare with the referenced issue #174456 to check whether the failure is recurring. Done means the test passes reliably, including with race detection.

Written by the indexing model from the issue text.