feat(web-basics): enhance demo components with improved UI and functionality

- Update WebTechTriad component with clearer labels and better visual hierarchy
- Improve Flexbox demo with axis visualization and more comprehensive controls
- Enhance BoxModel demo with box-sizing toggle and real-world scenario
- Refactor DomManipulator with expanded operations and code examples
- Add consistent styling and responsive design across all components

docs/.vitepress/theme/components/appendix/web-basics/CssBoxModel.vue

@@ -1,39 +1,65 @@
 <template>
   <div class="box-demo">
     <div class="demo-header">
-      <span class="icon">📦</span>
       <span class="title">CSS 盒模型</span>
-      <span class="subtitle">理解元素尺寸的构成</span>
+      <span class="subtitle">理解元素实际占用空间的构成</span>
+    </div>
+
+    <div class="scenario">
+      <strong>场景：</strong>你要做三个并排卡片，容器宽度 900px，每个卡片设 width: 200px。结果第三个掉下去了——为什么？
     </div>
 
     <div class="main-area">
       <div class="left-panel">
         <div class="controls">
           <div class="control-row">
-            <label>Padding</label>
+            <label>width</label>
+            <input type="range" min="60" max="150" v-model.number="contentW" />
+            <span class="val">{{ contentW }}px</span>
+          </div>
+          <div class="control-row">
+            <label>padding</label>
             <input type="range" min="0" max="30" v-model.number="padding" />
             <span class="val">{{ padding }}px</span>
           </div>
           <div class="control-row">
-            <label>Border</label>
-            <input type="range" min="0" max="20" v-model.number="border" />
+            <label>border</label>
+            <input type="range" min="0" max="15" v-model.number="border" />
             <span class="val">{{ border }}px</span>
           </div>
           <div class="control-row">
-            <label>Margin</label>
-            <input type="range" min="0" max="30" v-model.number="margin" />
+            <label>margin</label>
+            <input type="range" min="0" max="20" v-model.number="margin" />
             <span class="val">{{ margin }}px</span>
           </div>
         </div>
 
+        <div class="box-sizing-toggle">
+          <span class="toggle-label">box-sizing:</span>
+          <button 
+            :class="['toggle-btn', { active: boxSizing === 'content-box' }]"
+            @click="boxSizing = 'content-box'"
+          >
+            content-box
+          </button>
+          <button 
+            :class="['toggle-btn', { active: boxSizing === 'border-box' }]"
+            @click="boxSizing = 'border-box'"
+          >
+            border-box
+          </button>
+        </div>
+
         <div class="visual">
           <div class="layer margin" :style="{ padding: margin + 'px' }">
-            <span class="label" v-if="margin >= 10">Margin</span>
+            <span class="layer-label" v-if="margin >= 8">margin</span>
             <div class="layer border" :style="{ borderWidth: border + 'px' }">
-              <span class="label" v-if="border >= 8">Border</span>
+              <span class="layer-label" v-if="border >= 5">border</span>
               <div class="layer padding" :style="{ padding: padding + 'px' }">
-                <span class="label" v-if="padding >= 10">Padding</span>
-                <div class="content">内容</div>
+                <span class="layer-label" v-if="padding >= 8">padding</span>
+                <div class="content" :style="{ width: contentW + 'px' }">
+                  content<br>{{ contentW }}px
+                </div>
               </div>
             </div>
           </div>
@@ -41,21 +67,37 @@
       </div>
 
       <div class="right-panel">
-        <div class="result">
-          <div class="result-row">
-            <span class="result-label">总宽度：</span>
+        <div class="result-card">
+          <div class="result-header">
+            <span class="result-title">实际占用宽度</span>
             <span class="result-value">{{ total }}px</span>
           </div>
-          <div class="formula">= {{ margin }}×2 + {{ border }}×2 + {{ padding }}×2 + {{ contentW }}</div>
+          <div class="formula">
+            <template v-if="boxSizing === 'content-box'">
+              {{ contentW }} + {{ padding }}×2 + {{ border }}×2 + {{ margin }}×2 = {{ total }}px
+            </template>
+            <template v-else>
+              {{ contentW }}px（已包含 padding 和 border） + {{ margin }}×2 = {{ total }}px
+            </template>
+          </div>
+          <div class="result-hint" :class="{ warning: total * 3 > 900 }">
+            <template v-if="total * 3 > 900">
+              三个卡片需要 {{ total * 3 }}px，超出容器 900px，第三个会掉下去
+            </template>
+            <template v-else>
+              三个卡片共 {{ total * 3 }}px，可以放下
+            </template>
+          </div>
         </div>
 
         <div class="code-block">
           <div class="code-title">CSS</div>
           <div class="code-content">
             <div class="line">.box {</div>
+            <div class="line hl">  box-sizing: {{ boxSizing }};</div>
             <div class="line">  width: {{ contentW }}px;</div>
             <div class="line">  padding: {{ padding }}px;</div>
-            <div class="line">  border: {{ border }}px solid;</div>
+            <div class="line">  border: {{ border }}px solid #ccc;</div>
             <div class="line">  margin: {{ margin }}px;</div>
             <div class="line">}</div>
           </div>
@@ -64,8 +106,9 @@
     </div>
 
     <div class="info-box">
-      <span class="icon">💡</span>
-      <strong>核心思想：</strong>元素实际占用宽度 = 内容宽 + padding×2 + border×2 + margin×2
+      <strong>关键区别：</strong>
+      <code>content-box</code>（默认）的 width 只是内容宽度；
+      <code>border-box</code> 的 width 包含 content + padding + border。推荐全局设置 <code>box-sizing: border-box</code>。
     </div>
   </div>
 </template>
@@ -73,41 +116,66 @@
 <script setup>
 import { computed, ref } from 'vue'
 
-const contentW = 80
+const contentW = ref(100)
 const padding = ref(15)
-const border = ref(8)
-const margin = ref(15)
+const border = ref(5)
+const margin = ref(10)
+const boxSizing = ref('content-box')
 
-const total = computed(
-  () => margin.value * 2 + border.value * 2 + padding.value * 2 + contentW
-)
+const total = computed(() => {
+  if (boxSizing.value === 'border-box') {
+    return contentW.value + margin.value * 2
+  }
+  return contentW.value + padding.value * 2 + border.value * 2 + margin.value * 2
+})
 </script>
 
 <style scoped>
 .box-demo {
   border: 1px solid var(--vp-c-divider);
-  border-radius: 6px;
+  border-radius: 8px;
   background: var(--vp-c-bg-soft);
-  padding: 0.75rem;
-  margin: 0.5rem 0;
+  padding: 1rem;
+  margin: 1rem 0;
 }
 
 .demo-header {
   display: flex;
-  align-items: center;
-  gap: 0.5rem;
+  flex-direction: column;
+  gap: 0.25rem;
   margin-bottom: 0.75rem;
 }
 
-.demo-header .icon { font-size: 1.25rem; }
-.demo-header .title { font-weight: bold; font-size: 1rem; }
-.demo-header .subtitle { color: var(--vp-c-text-2); font-size: 0.85rem; margin-left: 0.5rem; }
+.demo-header .title {
+  font-weight: 600;
+  font-size: 1rem;
+  color: var(--vp-c-text-1);
+}
+
+.demo-header .subtitle {
+  color: var(--vp-c-text-2);
+  font-size: 0.85rem;
+}
+
+.scenario {
+  background: var(--vp-c-warning-soft);
+  border: 1px solid var(--vp-c-warning-dimm);
+  border-radius: 6px;
+  padding: 0.6rem 0.75rem;
+  font-size: 0.8rem;
+  color: var(--vp-c-text-2);
+  margin-bottom: 1rem;
+}
+
+.scenario strong {
+  color: var(--vp-c-text-1);
+}
 
 .main-area {
   display: grid;
   grid-template-columns: 1fr 1fr;
   gap: 1rem;
-  margin-bottom: 0.75rem;
+  margin-bottom: 1rem;
 }
 
 @media (max-width: 768px) {
@@ -138,9 +206,10 @@ const total = computed(
 
 .control-row label {
   font-size: 0.8rem;
-  font-weight: 600;
+  font-weight: 500;
   min-width: 55px;
   color: var(--vp-c-text-1);
+  font-family: var(--vp-font-family-mono);
 }
 
 .control-row input[type='range'] {
@@ -153,18 +222,51 @@ const total = computed(
   font-family: var(--vp-font-family-mono);
   font-size: 0.75rem;
   color: var(--vp-c-brand);
-  min-width: 35px;
+  min-width: 40px;
   text-align: right;
 }
 
+.box-sizing-toggle {
+  display: flex;
+  align-items: center;
+  gap: 0.5rem;
+  flex-wrap: wrap;
+}
+
+.toggle-label {
+  font-size: 0.8rem;
+  font-weight: 500;
+  color: var(--vp-c-text-2);
+  font-family: var(--vp-font-family-mono);
+}
+
+.toggle-btn {
+  padding: 0.3rem 0.6rem;
+  border: 1px solid var(--vp-c-divider);
+  border-radius: 4px;
+  background: var(--vp-c-bg);
+  cursor: pointer;
+  font-size: 0.7rem;
+  font-family: var(--vp-font-family-mono);
+  transition: all 0.2s;
+}
+
+.toggle-btn:hover { background: var(--vp-c-bg-soft); }
+.toggle-btn.active {
+  border-color: var(--vp-c-brand);
+  color: var(--vp-c-brand);
+  background: var(--vp-c-brand-soft);
+}
+
 .visual {
   background: var(--vp-c-bg);
   border: 1px solid var(--vp-c-divider);
-  border-radius: 6px;
-  padding: 0.75rem;
+  border-radius: 8px;
+  padding: 1rem;
   display: flex;
   justify-content: center;
   align-items: center;
+  min-height: 140px;
 }
 
 .layer {
@@ -176,90 +278,111 @@ const total = computed(
   transition: all 0.2s;
 }
 
-.layer .label {
+.layer-label {
   position: absolute;
   top: 2px;
   left: 4px;
   font-size: 9px;
-  font-weight: 700;
-  opacity: 0.7;
+  font-weight: 600;
+  opacity: 0.6;
+  font-family: var(--vp-font-family-mono);
 }
 
 .margin {
-  background: var(--vp-c-bg-soft);
-  border: 1px dashed var(--vp-c-divider);
+  background: rgba(251, 191, 36, 0.1);
+  border: 1px dashed rgba(251, 191, 36, 0.5);
 }
-.margin .label { color: var(--vp-c-text-3); }
+.margin .layer-label { color: #d97706; }
 
 .border {
-  background: var(--vp-c-brand-soft);
+  background: rgba(14, 165, 233, 0.1);
   border-style: solid;
   border-color: var(--vp-c-brand);
 }
-.border .label { color: var(--vp-c-brand-1); }
+.border .layer-label { color: var(--vp-c-brand); }
 
 .padding {
-  background: var(--vp-c-bg-alt);
-  border: 1px dashed var(--vp-c-divider);
+  background: rgba(34, 197, 94, 0.1);
+  border: 1px dashed rgba(34, 197, 94, 0.5);
 }
-.padding .label { color: var(--vp-c-text-2); }
+.padding .layer-label { color: #16a34a; }
 
 .content {
   background: var(--vp-c-brand);
   color: #fff;
   border-radius: 4px;
-  font-weight: 700;
-  font-size: 0.75rem;
-  width: 80px;
+  font-weight: 600;
+  font-size: 0.7rem;
   height: 50px;
   display: flex;
+  flex-direction: column;
   align-items: center;
   justify-content: center;
+  text-align: center;
+  line-height: 1.3;
 }
 
 .right-panel {
   display: flex;
   flex-direction: column;
-  gap: 0.5rem;
+  gap: 0.75rem;
 }
 
-.result {
+.result-card {
   background: var(--vp-c-bg);
   border: 1px solid var(--vp-c-divider);
-  border-radius: 6px;
-  padding: 0.6rem;
+  border-radius: 8px;
+  padding: 0.75rem;
 }
 
-.result-row {
+.result-header {
   display: flex;
   align-items: center;
-  gap: 0.5rem;
+  justify-content: space-between;
+  margin-bottom: 0.25rem;
 }
 
-.result-label {
-  font-size: 0.85rem;
-  font-weight: 600;
-  color: var(--vp-c-text-1);
+.result-title {
+  font-size: 0.8rem;
+  font-weight: 500;
+  color: var(--vp-c-text-2);
 }
 
 .result-value {
-  font-size: 1.1rem;
+  font-size: 1.25rem;
   font-weight: 700;
   color: var(--vp-c-brand);
+  font-family: var(--vp-font-family-mono);
 }
 
 .formula {
   font-family: var(--vp-font-family-mono);
   font-size: 0.75rem;
   color: var(--vp-c-text-2);
-  margin-top: 0.25rem;
+  background: var(--vp-c-bg-soft);
+  padding: 0.4rem 0.6rem;
+  border-radius: 4px;
+}
+
+.result-hint {
+  margin-top: 0.5rem;
+  font-size: 0.75rem;
+  color: var(--vp-c-success);
+  padding: 0.4rem 0.6rem;
+  background: var(--vp-c-success-soft);
+  border-radius: 4px;
+}
+
+.result-hint.warning {
+  color: var(--vp-c-warning);
+  background: var(--vp-c-warning-soft);
 }
 
 .code-block {
   background: var(--vp-c-bg);
   border: 1px solid var(--vp-c-divider);
-  border-radius: 6px;
-  padding: 0.6rem;
+  border-radius: 8px;
+  padding: 0.75rem;
   flex: 1;
 }
 
@@ -267,31 +390,39 @@ const total = computed(
   font-size: 0.75rem;
   font-weight: 600;
   color: var(--vp-c-text-2);
-  margin-bottom: 0.4rem;
+  margin-bottom: 0.5rem;
+  text-transform: uppercase;
+  letter-spacing: 0.5px;
 }
 
 .code-content {
-  background: #0b1221;
+  background: #1a1a2e;
   color: #e5e7eb;
-  border-radius: 4px;
-  padding: 0.5rem;
+  border-radius: 6px;
+  padding: 0.75rem;
   font-family: var(--vp-font-family-mono);
-  font-size: 0.7rem;
-  line-height: 1.5;
+  font-size: 0.75rem;
+  line-height: 1.6;
 }
 
 .line { white-space: pre; }
+.hl {
+  color: var(--vp-c-brand);
+}
 
 .info-box {
   background: var(--vp-c-bg-alt);
-  padding: 0.6rem;
-  border-radius: 6px;
+  padding: 0.75rem 1rem;
+  border-radius: 8px;
   font-size: 0.85rem;
   color: var(--vp-c-text-2);
-  display: flex;
-  gap: 0.25rem;
 }
 
-.info-box .icon { flex-shrink: 0; }
 .info-box strong { color: var(--vp-c-text-1); }
+.info-box code {
+  background: var(--vp-c-bg-soft);
+  padding: 0.1rem 0.3rem;
+  border-radius: 3px;
+  font-size: 0.8rem;
+}
 </style>