feat: enhance VLM response parsing and DOUBAO model support

- Fix JSON extraction logic by prioritizing brace counting method
- Add support for DOUBAO string array coordinate format
- Introduce IS_UI_TARS helper function for model type checking
- Add comprehensive tests for JSON parsing and coordinate handling
- Improve error handling with retry delays for LLM service failures

uixt/ai/utils_test.go

@@ -0,0 +1,79 @@
+package ai
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestExtractJSONFromContent(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{
+			name:     "valid JSON",
+			input:    `{"content": "test", "thought": "test"}`,
+			expected: `{"content": "test", "thought": "test"}`,
+		},
+		{
+			name:  "JSON in markdown",
+			input: "```json\n{\n  \"content\": \"test\"\n}\n```",
+			expected: `{
+  "content": "test"
+}`,
+		},
+		{
+			name:     "incomplete JSON without closing brace",
+			input:    `{"content": "incomplete json"`,
+			expected: "",
+		},
+		{
+			name:     "incomplete JSON with missing closing brace",
+			input:    `{"content": "incomplete json", "missing_closing_brace": true`,
+			expected: "",
+		},
+		{
+			name:     "plain text",
+			input:    "This is just plain text",
+			expected: "",
+		},
+		{
+			name: "complex nested JSON with arrays",
+			input: `{
+  "actions": [
+    {
+      "action_type": "click",
+      "action_inputs": {
+        "start_box": [371, 235, 425, 270]
+      }
+    }
+  ],
+  "thought": "点击桌面上的抖音应用图标以启动抖音",
+  "error": null
+}`,
+			expected: `{
+  "actions": [
+    {
+      "action_type": "click",
+      "action_inputs": {
+        "start_box": [371, 235, 425, 270]
+      }
+    }
+  ],
+  "thought": "点击桌面上的抖音应用图标以启动抖音",
+  "error": null
+}`,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := extractJSONFromContent(tt.input)
+			t.Logf("Input: %s", tt.input)
+			t.Logf("Output: %s", result)
+			assert.Equal(t, tt.expected, result)
+		})
+	}
+}