fix(build): 修复网关构建失败并收口候选选择与 finalize 回归

- 补齐 DecisionTraceCandidate 新增字段，修复审计测试构造
- 修正 usage 内存仓库的 created_at_unix_ms 字段引用与秒/毫秒换算
- 将 build_minimal_candidate_selection 重构为输入对象，消除 clippy 参数过多问题
- 修复 admin global model created_at 旧字段残留引用
- 修复 openai:cli 与 openai:compact 同家族 finalize 在 needs_conversion=true 时的成功回落逻辑
- 清理 aether-gateway 中的 derive/default 与 needless borrow 等 clippy 问题

apps/aether-gateway/src/execution_runtime/stream/execution.rs

@@ -790,7 +790,6 @@ async fn execute_stream_from_frame_stream(
     let request_id_for_report = request_id.to_string();
     let request_id_for_report_log = short_request_id(request_id);
     let candidate_id_for_report = candidate_id.map(ToOwned::to_owned);
-    let mut buffered_frames = buffered_frames;
     tokio::spawn(async move {
         let mut provider_buffered_body = provider_prefetched_body_for_report;
         let mut buffered_body = prefetched_body_for_report;