feat: enable text auto-wrap for text boxes by default

- Set text_frame.word_wrap = True in add_text_element() for PPTX
- Change CSS from white-space: pre-wrap to normal in HTML preview
- Add overflow-wrap: break-word for better word breaking
- Update README.md with auto-wrap documentation
- Update element-rendering and html-rendering specs
- Archive change: 2026-03-02-add-text-auto-wrap

yaml2pptx.py

@@ -406,6 +406,8 @@ def add_text_element(slide, elem, base_path=None):
     textbox = slide.shapes.add_textbox(x, y, w, h)
     tf = textbox.text_frame
     tf.text = elem.get('content', '')
+    # 默认启用文字自动换行
+    tf.word_wrap = True
 
     # 应用字体样式
     font_style = elem.get('font', {})
@@ -899,7 +901,8 @@ def render_text_element_to_html(elem):
         {'font-style: italic;' if font.get('italic') else ''}
         display: flex;
         align-items: center;
-        white-space: pre-wrap;
+        white-space: normal;
+        overflow-wrap: break-word;
     """
 
     content = elem.get('content', '').replace('<', '&lt;').replace('>', '&gt;')