fix: address lint errors

backend/internal/pkg/antigravity/gemini_types.go

@@ -143,10 +143,10 @@ type GeminiResponse struct {
 
 // GeminiCandidate Gemini 候选响应
 type GeminiCandidate struct {
-	Content            *GeminiContent           `json:"content,omitempty"`
-	FinishReason       string                   `json:"finishReason,omitempty"`
-	Index              int                      `json:"index,omitempty"`
-	GroundingMetadata  *GeminiGroundingMetadata `json:"groundingMetadata,omitempty"`
+	Content           *GeminiContent           `json:"content,omitempty"`
+	FinishReason      string                   `json:"finishReason,omitempty"`
+	Index             int                      `json:"index,omitempty"`
+	GroundingMetadata *GeminiGroundingMetadata `json:"groundingMetadata,omitempty"`
 }
 
 // GeminiUsageMetadata Gemini 用量元数据

backend/internal/pkg/antigravity/response_transformer.go

@@ -289,8 +289,8 @@ func buildGroundingText(grounding *GeminiGroundingMetadata) string {
 	var builder strings.Builder
 
 	if len(grounding.WebSearchQueries) > 0 {
-		builder.WriteString("\n\n---\nWeb search queries: ")
-		builder.WriteString(strings.Join(grounding.WebSearchQueries, ", "))
+		_, _ = builder.WriteString("\n\n---\nWeb search queries: ")
+		_, _ = builder.WriteString(strings.Join(grounding.WebSearchQueries, ", "))
 	}
 
 	if len(grounding.GroundingChunks) > 0 {
@@ -311,8 +311,8 @@ func buildGroundingText(grounding *GeminiGroundingMetadata) string {
 		}
 
 		if len(links) > 0 {
-			builder.WriteString("\n\nSources:\n")
-			builder.WriteString(strings.Join(links, "\n"))
+			_, _ = builder.WriteString("\n\nSources:\n")
+			_, _ = builder.WriteString(strings.Join(links, "\n"))
 		}
 	}