refactor(gateway): 重构格式转换候选资格检查并优化测试基础设施

- 将 format_conversion_disabled 的过滤提前到候选遴选阶段，替代原来的 skip_reason 标记机制
- 为测试添加 execution_runtime_sync_override 直接注入支持，避免启动额外 HTTP 服务器
- 将 submit_terminal_event 改为 async record_terminal_event 确保失败用量事件可靠入库
- 新增 test_support 模块封装可重试的 loopback 端口绑定逻辑
- 前端：poolTrace 将 skipped 从隐藏状态移除，新增 buildPoolParticipatedCandidates 统一新旧链路逻辑，并将 skipped 状态色改为 foreground

apps/aether-gateway/src/test_support.rs

@@ -0,0 +1,39 @@
+use std::io;
+use std::time::Duration;
+
+const LOOPBACK_BIND_MAX_ATTEMPTS: usize = 120;
+const LOOPBACK_BIND_RETRY_DELAY: Duration = Duration::from_millis(50);
+
+pub(crate) async fn bind_loopback_listener() -> io::Result<tokio::net::TcpListener> {
+    let mut last_retryable_error = None;
+
+    for attempt in 1..=LOOPBACK_BIND_MAX_ATTEMPTS {
+        match tokio::net::TcpListener::bind("127.0.0.1:0").await {
+            Ok(listener) => return Ok(listener),
+            Err(err)
+                if attempt < LOOPBACK_BIND_MAX_ATTEMPTS
+                    && is_retryable_loopback_bind_error(&err) =>
+            {
+                last_retryable_error = Some(err);
+                tokio::time::sleep(LOOPBACK_BIND_RETRY_DELAY).await;
+            }
+            Err(err) => return Err(err),
+        }
+    }
+
+    let err =
+        last_retryable_error.expect("loopback bind retries should record the last retryable error");
+    Err(io::Error::new(
+        err.kind(),
+        format!("loopback bind failed after {LOOPBACK_BIND_MAX_ATTEMPTS} attempts: {err}"),
+    ))
+}
+
+fn is_retryable_loopback_bind_error(err: &io::Error) -> bool {
+    matches!(
+        err.kind(),
+        io::ErrorKind::PermissionDenied
+            | io::ErrorKind::AddrInUse
+            | io::ErrorKind::AddrNotAvailable
+    )
+}