fix(clients): preserve gemini tool call responses

apps/api/internal/clients/gemini.go

@@ -265,7 +265,7 @@ func geminiResult(request Request, raw map[string]any) map[string]any {
 			"raw":     raw,
 		}
 	}
-	content := geminiText(raw)
+	message, finishReason := geminiChatMessage(raw)
 	return map[string]any{
 		"id":      "gemini-chat",
 		"object":  "chat.completion",
@@ -273,8 +273,8 @@ func geminiResult(request Request, raw map[string]any) map[string]any {
 		"model":   request.Model,
 		"choices": []any{map[string]any{
 			"index":         0,
-			"finish_reason": "stop",
-			"message":       map[string]any{"role": "assistant", "content": content},
+			"finish_reason": finishReason,
+			"message":       message,
 		}},
 		"usage": geminiUsageMap(raw),
 		"raw":   raw,
@@ -303,19 +303,59 @@ func textFromMessages(body map[string]any) string {
 }
 
 func geminiText(raw map[string]any) string {
+	message, _ := geminiChatMessage(raw)
+	content, _ := message["content"].(string)
+	return content
+}
+
+func geminiChatMessage(raw map[string]any) (map[string]any, string) {
 	candidates, _ := raw["candidates"].([]any)
 	for _, candidate := range candidates {
 		candidateMap, _ := candidate.(map[string]any)
 		content, _ := candidateMap["content"].(map[string]any)
 		parts, _ := content["parts"].([]any)
+		textParts := make([]string, 0, len(parts))
+		toolCalls := make([]any, 0)
 		for _, part := range parts {
 			partMap, _ := part.(map[string]any)
 			if text, ok := partMap["text"].(string); ok && text != "" {
-				return text
+				textParts = append(textParts, text)
+			}
+			functionCall := mapFromAny(firstPresent(partMap["functionCall"], partMap["function_call"]))
+			if len(functionCall) == 0 {
+				continue
+			}
+			if toolCall := normalizeGeminiFunctionCall(functionCall, len(toolCalls), false); toolCall != nil {
+				toolCalls = append(toolCalls, toolCall)
 			}
 		}
+		message := map[string]any{
+			"role":    "assistant",
+			"content": strings.Join(textParts, ""),
+		}
+		if len(toolCalls) > 0 {
+			message["tool_calls"] = toolCalls
+			if len(textParts) == 0 {
+				message["content"] = nil
+			}
+		}
+		return message, geminiFinishReason(candidateMap, len(toolCalls) > 0)
+	}
+	return map[string]any{"role": "assistant", "content": ""}, "stop"
+}
+
+func geminiFinishReason(candidate map[string]any, hasToolCalls bool) string {
+	if hasToolCalls {
+		return "tool_calls"
+	}
+	switch strings.ToUpper(stringFromAny(candidate["finishReason"])) {
+	case "MAX_TOKENS":
+		return "length"
+	case "SAFETY", "RECITATION", "BLOCKLIST", "PROHIBITED_CONTENT", "SPII":
+		return "content_filter"
+	default:
+		return "stop"
 	}
-	return ""
 }
 
 func geminiImageData(raw map[string]any) []any {