**4 issues found** across 16 files

Prompt for AI agents (unresolved issues)

```text Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately. P2: Remove the unused `EnqueueError` import; with Ruff `F` rules enabled this triggers `F401` and can fail CI. P1: Proto field number reuse: `messages` moved from field 2 → 1, reusing the deleted `message` field's number. During a rolling deployment, an old server writing `repeated messages` on field 2 will be silently ignored by new clients reading field 1. Keep `messages` at field number 2 and reserve field 1 to maintain wire compatibility. P3: `EnqueueError`'s new docstring contradicts runtime behavior: per-message enqueue failures can raise `EnqueueError` via `_map_enqueue_result_error` fallback. P2: The single-flush success test became too weak by only asserting call count; it should assert the actual request content sent to `Enqueue`. ```

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