fix(provider): 延长媒体超时并终止超时轮转

将图像和视频的默认 HTTP/轮询超时分别提高到 20 分钟和 30 分钟。媒体任务超时后直接失败，不再重试、切换客户端或标记为 upstream_submission_unknown。OpenAI 图像端点遇到上游明确拒绝 response_format 时自动移除并缓存兼容结论。

验证：go test ./... -count=1；go vet ./...；gofmt；相关 Shell bash -n、ShellCheck 与发布脚本回归测试。

apps/api/internal/runner/retry_decision.go

@@ -63,6 +63,7 @@ type resolveCandidateFailureInput struct {
 	FailoverExpired   bool
 	Async             bool
 	DownstreamStarted bool
+	TaskKind          string
 }
 
 type priorityDemoteDecision struct {
@@ -150,6 +151,20 @@ func failoverDecisionForCandidate(runnerPolicy store.RunnerPolicy, candidate sto
 
 func resolveCandidateFailure(input resolveCandidateFailureInput) failureDecision {
 	info := failureInfoFromError(input.Err)
+	if terminalMediaTimeout(input.TaskKind, input.Err) {
+		return failureDecision{
+			Route:  "stop",
+			Effect: "none",
+			Reason: "media_timeout_terminal",
+			Match: policyRuleMatch{
+				Source: "gateway_media_timeout",
+				Policy: "terminalTimeout",
+				Rule:   "taskKind",
+				Value:  strings.TrimSpace(input.TaskKind),
+			},
+			Info: info,
+		}
+	}
 	if isResultPersistenceFailure(input.Err) {
 		return failureDecision{
 			Route:  "stop",
@@ -260,6 +275,12 @@ func resolveCandidateFailure(input resolveCandidateFailureInput) failureDecision
 	}
 }
 
+func terminalMediaTimeout(kind string, err error) bool {
+	kind = strings.TrimSpace(kind)
+	return (strings.HasPrefix(kind, "images.") || strings.HasPrefix(kind, "videos.")) &&
+		strings.EqualFold(strings.TrimSpace(clients.ErrorCode(err)), "timeout")
+}
+
 func failoverEffect(action string) string {
 	switch action {
 	case "cooldown_and_next":