feat: add YAML validation with check command and auto-validation

Implements comprehensive validation before PPTX conversion to catch errors early. Includes element-level validation (colors, fonts, table consistency) and system-level validation (geometry, resources). Supports standalone check command and automatic validation during conversion.

validators/resource.py

@@ -0,0 +1,122 @@
+"""
+资源验证器
+
+验证 YAML 文件引用的外部资源是否存在。
+"""
+
+from pathlib import Path
+from validators.result import ValidationIssue
+from loaders.yaml_loader import load_yaml_file, validate_template_yaml
+
+
+class ResourceValidator:
+    """资源验证器"""
+
+    def __init__(self, yaml_dir: Path, template_dir: Path = None):
+        """
+        初始化资源验证器
+
+        Args:
+            yaml_dir: YAML 文件所在目录
+            template_dir: 模板文件目录（可选）
+        """
+        self.yaml_dir = yaml_dir
+        self.template_dir = template_dir
+
+    def validate_image(self, element, slide_index: int, elem_index: int) -> list:
+        """
+        验证图片文件是否存在
+
+        Args:
+            element: 图片元素对象
+            slide_index: 幻灯片索引（从 1 开始）
+            elem_index: 元素索引（从 1 开始）
+
+        Returns:
+            验证问题列表
+        """
+        issues = []
+        location = f"幻灯片 {slide_index}, 元素 {elem_index}"
+
+        if not hasattr(element, 'src'):
+            return issues
+
+        src = element.src
+        if not src:
+            return issues
+
+        # 解析路径（支持相对路径和绝对路径）
+        src_path = Path(src)
+        if not src_path.is_absolute():
+            src_path = self.yaml_dir / src
+
+        # 检查文件是否存在
+        if not src_path.exists():
+            issues.append(ValidationIssue(
+                level="ERROR",
+                message=f"图片文件不存在: {src}",
+                location=location,
+                code="IMAGE_FILE_NOT_FOUND"
+            ))
+
+        return issues
+
+    def validate_template(self, slide_data: dict, slide_index: int) -> list:
+        """
+        验证模板文件是否存在且结构正确
+
+        Args:
+            slide_data: 幻灯片数据字典
+            slide_index: 幻灯片索引（从 1 开始）
+
+        Returns:
+            验证问题列表
+        """
+        issues = []
+        location = f"幻灯片 {slide_index}"
+
+        if 'template' not in slide_data:
+            return issues
+
+        template_name = slide_data['template']
+        if not template_name:
+            return issues
+
+        # 检查是否提供了模板目录
+        if not self.template_dir:
+            issues.append(ValidationIssue(
+                level="ERROR",
+                message=f"使用了模板但未指定模板目录: {template_name}",
+                location=location,
+                code="TEMPLATE_DIR_NOT_SPECIFIED"
+            ))
+            return issues
+
+        # 解析模板文件路径
+        template_path = self.template_dir / template_name
+        if not template_path.suffix:
+            template_path = template_path.with_suffix('.yaml')
+
+        # 检查模板文件是否存在
+        if not template_path.exists():
+            issues.append(ValidationIssue(
+                level="ERROR",
+                message=f"模板文件不存在: {template_name}",
+                location=location,
+                code="TEMPLATE_FILE_NOT_FOUND"
+            ))
+            return issues
+
+        # 验证模板文件结构
+        try:
+            template_data = load_yaml_file(template_path)
+            validate_template_yaml(template_data, str(template_path))
+        except Exception as e:
+            issues.append(ValidationIssue(
+                level="ERROR",
+                message=f"模板文件结构错误: {template_name} - {str(e)}",
+                location=location,
+                code="TEMPLATE_STRUCTURE_ERROR"
+            ))
+
+        return issues