fix: DynamicColumn子控件宽度覆盖为100%+修复间隙和覆盖问题

- _fix_children: MutationObserver监听子控件添加，强制width:100%+minWidth:0
- 解决子控件cwidth设置的固定像素宽度超出grid cell导致重叠
- align-items:start防止grid items垂直拉伸
- col_cgap默认值统一为1（原构造函数设0.5但set_column_width用0.1）
- 移除console.log调试输出

bricks/dynamiccolumn.js

@@ -15,22 +15,34 @@ bricks.DynamicColumn = class extends bricks.Layout {
 				opts.col_cwidth = 20;
 			}
 		}
-		opts.col_cgap = opts.col_cgap || 0.5;
+		opts.col_cgap = opts.col_cgap || 1;
 		opts.mobile_cols = opts.mobile_cols|| 1;
 		super(opts);
 		this.set_style('display', 'grid');
-		// this.set_column_width();
+		this.set_style('align-items', 'start');
 		this.bind('on_parent', this.set_column_width.bind(this));
 		this.bind('resize', this.set_column_width.bind(this));
 		if (this.cwidth){
 			bricks.app.bind('charsize', this.set_column_width.bind(this));
 		}
+		// Watch for new children added and fix their width
+		this._observer = new MutationObserver(this._fix_children.bind(this));
+		this._observer.observe(this.dom_element, {childList: true, subtree: false});
+	}
+	_fix_children(){
+		var children = this.dom_element.children;
+		for (var i=0; i<children.length; i++){
+			var el = children[i];
+			el.style.width = '100%';
+			el.style.minWidth = '0';
+			el.style.boxSizing = 'border-box';
+		}
 	}
 	set_column_width(){
 		var cw;
 		var cols;
 		var gap;
-		gap = bricks.app.charsize * (this.col_cgap || 0.1);
+		gap = bricks.app.charsize * (this.col_cgap || 1);
 		var width = bricks.app.screenWidth();
 		var height = bricks.app.screenHeight();
 		if (bricks.is_mobile() && width < height){
@@ -46,6 +58,8 @@ bricks.DynamicColumn = class extends bricks.Layout {
 		}
 		this.dom_element.style.gridTemplateColumns = "repeat(auto-fill, minmax(" + cw + "px, 1fr))";
 		this.set_style('gap', gap + 'px');
+		// Fix existing children widths
+		this._fix_children();
 	}
 }