fix(kiro): handle tool_use in content array for compaction requests

Problem:
- PR #162 fixed empty string content but missed array content with tool_use
- OpenCode's compaction requests send assistant messages with content as array
- When content array contains only tool_use (no text), content becomes empty
- This causes 'Improperly formed request' errors from Kiro API

Example of problematic message format:
{
  "role": "assistant",
  "content": [
    {"type": "tool_use", "id": "...", "name": "todowrite", "input": {...}}
  ]
}

Solution:
- Extract tool_use from content array (Anthropic/OpenCode format)
- This is in addition to existing tool_calls handling (OpenAI format)
- The empty content fallback from PR #162 will then work correctly

Fixes compaction failures that persisted after PR #162 merge.

internal/translator/kiro/openai/kiro_openai_request.go

@@ -659,13 +659,42 @@ func buildAssistantMessageFromOpenAI(msg gjson.Result) KiroAssistantResponseMess
 		contentBuilder.WriteString(content.String())
 	} else if content.IsArray() {
 		for _, part := range content.Array() {
-			if part.Get("type").String() == "text" {
+			partType := part.Get("type").String()
+			switch partType {
+			case "text":
 				contentBuilder.WriteString(part.Get("text").String())
+			case "tool_use":
+				// Handle tool_use in content array (Anthropic/OpenCode format)
+				// This is different from OpenAI's tool_calls format
+				toolUseID := part.Get("id").String()
+				toolName := part.Get("name").String()
+				inputData := part.Get("input")
+
+				var inputMap map[string]interface{}
+				if inputData.Exists() {
+					if inputData.IsObject() {
+						inputMap = make(map[string]interface{})
+						inputData.ForEach(func(key, value gjson.Result) bool {
+							inputMap[key.String()] = value.Value()
+							return true
+						})
+					}
+				}
+				if inputMap == nil {
+					inputMap = make(map[string]interface{})
+				}
+
+				toolUses = append(toolUses, KiroToolUse{
+					ToolUseID: toolUseID,
+					Name:      toolName,
+					Input:     inputMap,
+				})
+				log.Debugf("kiro-openai: extracted tool_use from content array: %s", toolName)
 			}
 		}
 	}
 
-	// Handle tool_calls
+	// Handle tool_calls (OpenAI format)
 	toolCalls := msg.Get("tool_calls")
 	if toolCalls.IsArray() {
 		for _, tc := range toolCalls.Array() {