feat(stream-bridge): 支持上游 sync 响应转 SSE 流式输出，记录 client/upstream 流模式差异

- 新增 sync_to_stream 桥接模块，将非 SSE 上游响应转换为 SSE 格式回传给流式客户端
- stream_pump 检测非 SSE 响应头后缓冲整包并通过桥接逻辑重写为 SSE 帧
- proxy handler 同步支持 sync→stream 聚合与转换（覆盖 openai/claude/gemini 四种格式）
- sync_products 补全 openai:cli 的完整流式事件聚合（text delta、reasoning、tool call 等）
- usage runtime 写入 client_requested_stream / upstream_is_stream 到 request_metadata
- SQL 查询层将两个布尔字段从 request_metadata jsonb 中提取并回传给前端
- 前端 status.ts 新增 resolveUsageStreamLabelSegments，优先读取 client_requested_stream
- RequestDetailDrawer 在流式转换场景下显示"客户端→上游"两段 Badge

crates/aether-usage-runtime/src/request_metadata.rs

@@ -68,6 +68,7 @@ pub(crate) fn sanitize_usage_request_metadata_ref(value: Option<&Value>) -> Opti
 fn copy_allowed_metadata_fields(source: &Map<String, Value>, target: &mut Map<String, Value>) {
     copy_non_empty_string(source, target, "trace_id");
     copy_bool(source, target, "client_requested_stream");
+    copy_bool(source, target, "upstream_is_stream");
     copy_number(source, target, "provider_request_body_base64_bytes");
     copy_number(source, target, "provider_response_body_base64_bytes");
     copy_number(source, target, "client_response_body_base64_bytes");
@@ -89,6 +90,7 @@ fn copy_allowed_metadata_fields(source: &Map<String, Value>, target: &mut Map<St
 fn move_allowed_metadata_fields(mut source: Map<String, Value>, target: &mut Map<String, Value>) {
     remove_non_empty_string(&mut source, target, "trace_id");
     remove_bool(&mut source, target, "client_requested_stream");
+    remove_bool(&mut source, target, "upstream_is_stream");
     remove_number(&mut source, target, "provider_request_body_base64_bytes");
     remove_number(&mut source, target, "provider_response_body_base64_bytes");
     remove_number(&mut source, target, "client_response_body_base64_bytes");
@@ -369,6 +371,7 @@ mod tests {
             "candidate_index": 2,
             "trace_id": "trace-1",
             "client_requested_stream": false,
+            "upstream_is_stream": true,
             "provider_request_body_base64_bytes": 512,
             "provider_response_body_base64_bytes": 1024,
             "client_response_body_base64_bytes": 2048,
@@ -395,6 +398,7 @@ mod tests {
             json!({
                 "trace_id": "trace-1",
                 "client_requested_stream": false,
+                "upstream_is_stream": true,
                 "provider_request_body_base64_bytes": 512,
                 "provider_response_body_base64_bytes": 1024,
                 "client_response_body_base64_bytes": 2048,
@@ -449,6 +453,7 @@ mod tests {
                     "request_id": "req-1",
                     "candidate_index": 0,
                     "client_requested_stream": false,
+                    "upstream_is_stream": true,
                     "provider_id": "provider-1",
                     "billing_snapshot": {"status": "complete"}
                 })
@@ -462,6 +467,7 @@ mod tests {
             metadata,
             json!({
                 "client_requested_stream": false,
+                "upstream_is_stream": true,
                 "billing_snapshot": {"status": "complete"}
             })
         );