Flaky test: cyphr-cli test_export_import_roundtrip fails ~10% of runs

`cyphr-cli`'s integration test `test_export_import_roundtrip` fails nondeterministically with a panic at integration.rs:185 ("list should succeed"), at roughly a 1-in-10 rate. Reproduced at a tip that predates the current server work (so it is not caused by it), both under `cargo test --workspace` and standalone.

Impact: any branch's workspace gate can go red for reasons unrelated to the branch, which erodes trust in the gate. Until fixed, a workspace failure in only this test warrants a rerun before assigning blame.

Suggested next step: make the failure deterministic enough to diagnose (capture the `list` command's stderr in the panic message, run the test serially or with an isolated data dir) — the panic currently discards the underlying error.

Start at integration.rs:185 and run test_export_import_roundtrip both standalone and through cargo test --workspace. Preserve the list command's stderr and investigate whether serialization or an isolated data directory changes the failure rate. Done means the underlying failure is diagnosable and the test passes reliably without unexplained workspace-gate failures.

Written by the indexing model from the issue text.