fix(backend): 修复 CI 失败问题

修复内容：
1. 修复 6 个 golangci-lint 错误
   - 3 个 errcheck 错误：在 gateway_request_test.go 中添加类型断言检查
   - 3 个 gofmt 格式化问题：修复代码格式
2. 修复 API 契约测试失败
   - 在测试中添加缺失的字段：enable_identity_patch 和 identity_patch_prompt

所有测试和 linter 检查现已通过。

backend/internal/server/api_contract_test.go

@@ -313,7 +313,9 @@ func TestAPIContracts(t *testing.T) {
 					"fallback_model_anthropic": "claude-3-5-sonnet-20241022",
 					"fallback_model_antigravity": "gemini-2.5-pro",
 					"fallback_model_gemini": "gemini-2.5-pro",
-					"fallback_model_openai": "gpt-4o"
+					"fallback_model_openai": "gpt-4o",
+					"enable_identity_patch": true,
+					"identity_patch_prompt": ""
 				}
 			}`,
 		},

backend/internal/service/antigravity_gateway_service_test.go

@@ -17,14 +17,14 @@ func TestStripSignatureSensitiveBlocksFromClaudeRequest(t *testing.T) {
 		},
 		Messages: []antigravity.ClaudeMessage{
 			{
-				Role:    "assistant",
+				Role: "assistant",
 				Content: json.RawMessage(`[
 					{"type":"thinking","thinking":"secret plan","signature":""},
 					{"type":"tool_use","id":"t1","name":"Bash","input":{"command":"ls"}}
 				]`),
 			},
 			{
-				Role:    "user",
+				Role: "user",
 				Content: json.RawMessage(`[
 					{"type":"tool_result","tool_use_id":"t1","content":"ok","is_error":false},
 					{"type":"redacted_thinking","data":"..."}

backend/internal/service/gateway_request.go

@@ -91,7 +91,7 @@ func FilterThinkingBlocks(body []byte) []byte {
 //   - Anthropic extended thinking has a structural constraint: when top-level `thinking` is enabled and the
 //     final message is an assistant prefill, the assistant content must start with a thinking block.
 //   - If we remove thinking blocks but keep top-level `thinking` enabled, we can trigger:
-//       "Expected `thinking` or `redacted_thinking`, but found `text`"
+//     "Expected `thinking` or `redacted_thinking`, but found `text`"
 //
 // Strategy (B: preserve content as text):
 //   - Disable top-level `thinking` (remove `thinking` field).

backend/internal/service/gateway_request_test.go

@@ -176,11 +176,14 @@ func TestFilterThinkingBlocksForRetry_DisablesThinkingAndPreservesAsText(t *test
 	require.True(t, ok)
 	require.Len(t, msgs, 2)
 
-	assistant := msgs[1].(map[string]any)
-	content := assistant["content"].([]any)
+	assistant, ok := msgs[1].(map[string]any)
+	require.True(t, ok)
+	content, ok := assistant["content"].([]any)
+	require.True(t, ok)
 	require.Len(t, content, 2)
 
-	first := content[0].(map[string]any)
+	first, ok := content[0].(map[string]any)
+	require.True(t, ok)
 	require.Equal(t, "text", first["type"])
 	require.Equal(t, "Let me think...", first["text"])
 }
@@ -221,11 +224,17 @@ func TestFilterThinkingBlocksForRetry_RemovesRedactedThinkingAndKeepsValidConten
 	_, hasThinking := req["thinking"]
 	require.False(t, hasThinking)
 
-	msgs := req["messages"].([]any)
-	content := msgs[0].(map[string]any)["content"].([]any)
+	msgs, ok := req["messages"].([]any)
+	require.True(t, ok)
+	msg0, ok := msgs[0].(map[string]any)
+	require.True(t, ok)
+	content, ok := msg0["content"].([]any)
+	require.True(t, ok)
 	require.Len(t, content, 1)
-	require.Equal(t, "text", content[0].(map[string]any)["type"])
-	require.Equal(t, "Visible", content[0].(map[string]any)["text"])
+	content0, ok := content[0].(map[string]any)
+	require.True(t, ok)
+	require.Equal(t, "text", content0["type"])
+	require.Equal(t, "Visible", content0["text"])
 }
 
 func TestFilterThinkingBlocksForRetry_EmptyContentGetsPlaceholder(t *testing.T) {
@@ -240,11 +249,17 @@ func TestFilterThinkingBlocksForRetry_EmptyContentGetsPlaceholder(t *testing.T)
 
 	var req map[string]any
 	require.NoError(t, json.Unmarshal(out, &req))
-	msgs := req["messages"].([]any)
-	content := msgs[0].(map[string]any)["content"].([]any)
+	msgs, ok := req["messages"].([]any)
+	require.True(t, ok)
+	msg0, ok := msgs[0].(map[string]any)
+	require.True(t, ok)
+	content, ok := msg0["content"].([]any)
+	require.True(t, ok)
 	require.Len(t, content, 1)
-	require.Equal(t, "text", content[0].(map[string]any)["type"])
-	require.NotEmpty(t, content[0].(map[string]any)["text"])
+	content0, ok := content[0].(map[string]any)
+	require.True(t, ok)
+	require.Equal(t, "text", content0["type"])
+	require.NotEmpty(t, content0["text"])
 }
 
 func TestFilterSignatureSensitiveBlocksForRetry_DowngradesTools(t *testing.T) {
@@ -265,11 +280,19 @@ func TestFilterSignatureSensitiveBlocksForRetry_DowngradesTools(t *testing.T) {
 	_, hasThinking := req["thinking"]
 	require.False(t, hasThinking)
 
-	msgs := req["messages"].([]any)
-	content := msgs[0].(map[string]any)["content"].([]any)
+	msgs, ok := req["messages"].([]any)
+	require.True(t, ok)
+	msg0, ok := msgs[0].(map[string]any)
+	require.True(t, ok)
+	content, ok := msg0["content"].([]any)
+	require.True(t, ok)
 	require.Len(t, content, 2)
-	require.Equal(t, "text", content[0].(map[string]any)["type"])
-	require.Equal(t, "text", content[1].(map[string]any)["type"])
-	require.Contains(t, content[0].(map[string]any)["text"], "tool_use")
-	require.Contains(t, content[1].(map[string]any)["text"], "tool_result")
+	content0, ok := content[0].(map[string]any)
+	require.True(t, ok)
+	content1, ok := content[1].(map[string]any)
+	require.True(t, ok)
+	require.Equal(t, "text", content0["type"])
+	require.Equal(t, "text", content1["type"])
+	require.Contains(t, content0["text"], "tool_use")
+	require.Contains(t, content1["text"], "tool_result")
 }

backend/internal/service/gateway_service.go

@@ -1135,90 +1135,90 @@ func (s *GatewayService) Forward(ctx context.Context, c *gin.Context, account *A
 		// 优先检测thinking block签名错误（400）并重试一次
 		if resp.StatusCode == 400 {
 			respBody, readErr := io.ReadAll(io.LimitReader(resp.Body, 2<<20))
-				if readErr == nil {
-					_ = resp.Body.Close()
-
-					if s.isThinkingBlockSignatureError(respBody) {
-						looksLikeToolSignatureError := func(msg string) bool {
-							m := strings.ToLower(msg)
-							return strings.Contains(m, "tool_use") ||
-								strings.Contains(m, "tool_result") ||
-								strings.Contains(m, "functioncall") ||
-								strings.Contains(m, "function_call") ||
-								strings.Contains(m, "functionresponse") ||
-								strings.Contains(m, "function_response")
-						}
+			if readErr == nil {
+				_ = resp.Body.Close()
 
-						// 避免在重试预算已耗尽时再发起额外请求
-						if time.Since(retryStart) >= maxRetryElapsed {
-							resp.Body = io.NopCloser(bytes.NewReader(respBody))
-							break
+				if s.isThinkingBlockSignatureError(respBody) {
+					looksLikeToolSignatureError := func(msg string) bool {
+						m := strings.ToLower(msg)
+						return strings.Contains(m, "tool_use") ||
+							strings.Contains(m, "tool_result") ||
+							strings.Contains(m, "functioncall") ||
+							strings.Contains(m, "function_call") ||
+							strings.Contains(m, "functionresponse") ||
+							strings.Contains(m, "function_response")
+					}
+
+					// 避免在重试预算已耗尽时再发起额外请求
+					if time.Since(retryStart) >= maxRetryElapsed {
+						resp.Body = io.NopCloser(bytes.NewReader(respBody))
+						break
 					}
 					log.Printf("Account %d: detected thinking block signature error, retrying with filtered thinking blocks", account.ID)
 
-						// Conservative two-stage fallback:
-						// 1) Disable thinking + thinking->text (preserve content)
-						// 2) Only if upstream still errors AND error message points to tool/function signature issues:
-						//    also downgrade tool_use/tool_result blocks to text.
-
-						filteredBody := FilterThinkingBlocksForRetry(body)
-						retryReq, buildErr := s.buildUpstreamRequest(ctx, c, account, filteredBody, token, tokenType, reqModel)
-						if buildErr == nil {
-							retryResp, retryErr := s.httpUpstream.Do(retryReq, proxyURL, account.ID, account.Concurrency)
-							if retryErr == nil {
-								if retryResp.StatusCode < 400 {
-									log.Printf("Account %d: signature error retry succeeded (thinking downgraded)", account.ID)
-									resp = retryResp
-									break
-								}
+					// Conservative two-stage fallback:
+					// 1) Disable thinking + thinking->text (preserve content)
+					// 2) Only if upstream still errors AND error message points to tool/function signature issues:
+					//    also downgrade tool_use/tool_result blocks to text.
+
+					filteredBody := FilterThinkingBlocksForRetry(body)
+					retryReq, buildErr := s.buildUpstreamRequest(ctx, c, account, filteredBody, token, tokenType, reqModel)
+					if buildErr == nil {
+						retryResp, retryErr := s.httpUpstream.Do(retryReq, proxyURL, account.ID, account.Concurrency)
+						if retryErr == nil {
+							if retryResp.StatusCode < 400 {
+								log.Printf("Account %d: signature error retry succeeded (thinking downgraded)", account.ID)
+								resp = retryResp
+								break
+							}
 
-								retryRespBody, retryReadErr := io.ReadAll(io.LimitReader(retryResp.Body, 2<<20))
-								_ = retryResp.Body.Close()
-								if retryReadErr == nil && retryResp.StatusCode == 400 && s.isThinkingBlockSignatureError(retryRespBody) {
-									msg2 := extractUpstreamErrorMessage(retryRespBody)
-									if looksLikeToolSignatureError(msg2) && time.Since(retryStart) < maxRetryElapsed {
-										log.Printf("Account %d: signature retry still failing and looks tool-related, retrying with tool blocks downgraded", account.ID)
-										filteredBody2 := FilterSignatureSensitiveBlocksForRetry(body)
-										retryReq2, buildErr2 := s.buildUpstreamRequest(ctx, c, account, filteredBody2, token, tokenType, reqModel)
-										if buildErr2 == nil {
-											retryResp2, retryErr2 := s.httpUpstream.Do(retryReq2, proxyURL, account.ID, account.Concurrency)
-											if retryErr2 == nil {
-												resp = retryResp2
-												break
-											}
-											if retryResp2 != nil && retryResp2.Body != nil {
-												_ = retryResp2.Body.Close()
-											}
-											log.Printf("Account %d: tool-downgrade signature retry failed: %v", account.ID, retryErr2)
-										} else {
-											log.Printf("Account %d: tool-downgrade signature retry build failed: %v", account.ID, buildErr2)
+							retryRespBody, retryReadErr := io.ReadAll(io.LimitReader(retryResp.Body, 2<<20))
+							_ = retryResp.Body.Close()
+							if retryReadErr == nil && retryResp.StatusCode == 400 && s.isThinkingBlockSignatureError(retryRespBody) {
+								msg2 := extractUpstreamErrorMessage(retryRespBody)
+								if looksLikeToolSignatureError(msg2) && time.Since(retryStart) < maxRetryElapsed {
+									log.Printf("Account %d: signature retry still failing and looks tool-related, retrying with tool blocks downgraded", account.ID)
+									filteredBody2 := FilterSignatureSensitiveBlocksForRetry(body)
+									retryReq2, buildErr2 := s.buildUpstreamRequest(ctx, c, account, filteredBody2, token, tokenType, reqModel)
+									if buildErr2 == nil {
+										retryResp2, retryErr2 := s.httpUpstream.Do(retryReq2, proxyURL, account.ID, account.Concurrency)
+										if retryErr2 == nil {
+											resp = retryResp2
+											break
+										}
+										if retryResp2 != nil && retryResp2.Body != nil {
+											_ = retryResp2.Body.Close()
 										}
+										log.Printf("Account %d: tool-downgrade signature retry failed: %v", account.ID, retryErr2)
+									} else {
+										log.Printf("Account %d: tool-downgrade signature retry build failed: %v", account.ID, buildErr2)
 									}
 								}
-
-								// Fall back to the original retry response context.
-								resp = &http.Response{
-									StatusCode: retryResp.StatusCode,
-									Header:     retryResp.Header.Clone(),
-									Body:       io.NopCloser(bytes.NewReader(retryRespBody)),
-								}
-								break
 							}
-							if retryResp != nil && retryResp.Body != nil {
-								_ = retryResp.Body.Close()
+
+							// Fall back to the original retry response context.
+							resp = &http.Response{
+								StatusCode: retryResp.StatusCode,
+								Header:     retryResp.Header.Clone(),
+								Body:       io.NopCloser(bytes.NewReader(retryRespBody)),
 							}
-							log.Printf("Account %d: signature error retry failed: %v", account.ID, retryErr)
-						} else {
-							log.Printf("Account %d: signature error retry build request failed: %v", account.ID, buildErr)
+							break
 						}
-
-						// Retry failed: restore original response body and continue handling.
-						resp.Body = io.NopCloser(bytes.NewReader(respBody))
-						break
+						if retryResp != nil && retryResp.Body != nil {
+							_ = retryResp.Body.Close()
+						}
+						log.Printf("Account %d: signature error retry failed: %v", account.ID, retryErr)
+					} else {
+						log.Printf("Account %d: signature error retry build request failed: %v", account.ID, buildErr)
 					}
-					// 不是thinking签名错误，恢复响应体
+
+					// Retry failed: restore original response body and continue handling.
 					resp.Body = io.NopCloser(bytes.NewReader(respBody))
+					break
 				}
+				// 不是thinking签名错误，恢复响应体
+				resp.Body = io.NopCloser(bytes.NewReader(respBody))
+			}
 		}
 
 		// 检查是否需要通用重试（排除400，因为400已经在上面特殊处理过了）