feat(openai): 完善 Chat 与 Responses 参数转发

原生 Chat/Responses 改为透明转发，保留标准工具结构并保护调用方显式参数。补齐 Responses 到 Chat 的兼容转换、协议路由边界、完整响应和流式事件，并同步更新 Swagger、回归测试与真实验收脚本。

验证：
- cd apps/api && env -u AI_GATEWAY_TEST_DATABASE_URL go test ./... -count=1
- pnpm openapi
- pnpm lint
- pnpm test
- pnpm build
- gofmt -l 无输出
- git diff --check 通过

风险：
- Chat 回退无法等价表达的 Responses 原生能力现在会返回 unsupported_response_parameter
- 真实供应商 E2E 因本地没有已启用的平台模型候选而未完成

apps/api/internal/clients/openai_request_params.go

@@ -1,15 +1,9 @@
 package clients
 
-import (
-	"fmt"
-	"net/http"
-	"sort"
-)
-
 // Keep these lists aligned with openai-node 6.47.0 and the public OpenAI API
-// reference. The Gateway accepts a small, explicit set of routing extensions at
-// ingress, but only protocol fields (plus controlled provider adaptations) are
-// allowed across the upstream boundary.
+// reference. They document and test the currently known surface, but are not an
+// upstream allowlist: unknown fields may be introduced by OpenAI after a
+// Gateway release and must remain transparent.
 var openAIChatRequestParameters = stringSet(
 	"messages", "model", "audio", "frequency_penalty", "function_call", "functions",
 	"logit_bias", "logprobs", "max_completion_tokens", "max_tokens", "metadata",
@@ -50,56 +44,36 @@ var controlledOpenAIChatProviderParameters = stringSet(
 var controlledOpenAIResponsesProviderParameters = stringSet("presence_penalty", "frequency_penalty")
 
 func ValidateOpenAIRequestParameters(kind string, body map[string]any) error {
-	allowed := openAIChatRequestParameters
-	if kind == "responses" {
-		allowed = openAIResponsesRequestParameters
-	}
-	unknown := make([]string, 0)
-	for key := range body {
-		if _, ok := allowed[key]; ok {
-			continue
-		}
-		if _, ok := gatewayOpenAIRequestExtensions[key]; ok {
-			continue
-		}
-		if kind == "responses" {
-			if _, ok := gatewayResponsesRequestExtensions[key]; ok {
-				continue
-			}
-		}
-		unknown = append(unknown, key)
-	}
-	if len(unknown) == 0 {
-		return nil
-	}
-	sort.Strings(unknown)
-	return &ClientError{
-		Code:       "invalid_parameter",
-		Message:    fmt.Sprintf("Unknown parameter: %s", unknown[0]),
-		Param:      unknown[0],
-		StatusCode: http.StatusBadRequest,
-		Retryable:  false,
-	}
+	// OpenAI-compatible public endpoints intentionally accept future official
+	// fields. Provider validation remains authoritative for fields the selected
+	// upstream does not support.
+	_ = kind
+	_ = body
+	return nil
 }
 
 func FilterOpenAIChatRequestBody(body map[string]any) map[string]any {
-	return filterOpenAIRequestBody(body, openAIChatRequestParameters, controlledOpenAIChatProviderParameters)
+	return filterOpenAIRequestBody(body, controlledOpenAIChatProviderParameters, nil)
 }
 
 func FilterOpenAIResponsesRequestBody(body map[string]any) map[string]any {
-	return filterOpenAIRequestBody(body, openAIResponsesRequestParameters, controlledOpenAIResponsesProviderParameters)
+	return filterOpenAIRequestBody(body, controlledOpenAIResponsesProviderParameters, gatewayResponsesRequestExtensions)
 }
 
-func filterOpenAIRequestBody(body map[string]any, allowed map[string]struct{}, extensions map[string]struct{}) map[string]any {
+func filterOpenAIRequestBody(body map[string]any, controlled map[string]struct{}, protocolInternal map[string]struct{}) map[string]any {
 	out := make(map[string]any, len(body))
 	for key, value := range body {
-		if _, ok := allowed[key]; ok {
+		if _, ok := controlled[key]; ok {
 			out[key] = value
 			continue
 		}
-		if _, ok := extensions[key]; ok {
-			out[key] = value
+		if _, internal := gatewayOpenAIRequestExtensions[key]; internal {
+			continue
 		}
+		if _, internal := protocolInternal[key]; internal {
+			continue
+		}
+		out[key] = value
 	}
 	return out
 }