refactor: consolidate stream smoothing into StreamProcessor with intelligent timing

- Move StreamSmoother functionality directly into StreamProcessor for better integration
- Create ContentExtractor strategy pattern for format-agnostic content extraction
- Implement intelligent dynamic delay calculation based on text length
- Support three text length tiers: short (char-by-char), medium (chunked), long (chunked)
- Remove manual chunk_size and delay_ms configuration - now auto-calculated
- Simplify admin UI to single toggle switch with auto timing adjustment
- Extract format detection logic to reusable content_extractors module
- Improve code maintainability with cleaner architecture

frontend/src/views/admin/SystemSettings.vue

@@ -470,68 +470,20 @@
         title="流式输出"
         description="配置流式响应的输出效果"
       >
-        <div class="grid grid-cols-1 md:grid-cols-2 gap-6">
-          <div class="md:col-span-2">
-            <div class="flex items-center space-x-2">
-              <Checkbox
-                id="stream-smoothing-enabled"
-                v-model:checked="systemConfig.stream_smoothing_enabled"
-              />
-              <div>
-                <Label
-                  for="stream-smoothing-enabled"
-                  class="cursor-pointer"
-                >
-                  启用平滑输出
-                </Label>
-                <p class="text-xs text-muted-foreground">
-                  将上游返回的大块内容拆分成小块，模拟打字效果
-                </p>
-              </div>
-            </div>
-          </div>
-
+        <div class="flex items-center space-x-2">
+          <Checkbox
+            id="stream-smoothing-enabled"
+            v-model:checked="systemConfig.stream_smoothing_enabled"
+          />
           <div>
             <Label
-              for="stream-smoothing-chunk-size"
-              class="block text-sm font-medium"
+              for="stream-smoothing-enabled"
+              class="cursor-pointer"
             >
-              每块字符数
+              启用平滑输出
             </Label>
-            <Input
-              id="stream-smoothing-chunk-size"
-              v-model.number="systemConfig.stream_smoothing_chunk_size"
-              type="number"
-              min="1"
-              max="100"
-              placeholder="5"
-              class="mt-1"
-              :disabled="!systemConfig.stream_smoothing_enabled"
-            />
-            <p class="mt-1 text-xs text-muted-foreground">
-              每次输出的字符数量（1-100）
-            </p>
-          </div>
-
-          <div>
-            <Label
-              for="stream-smoothing-delay-ms"
-              class="block text-sm font-medium"
-            >
-              输出间隔 (毫秒)
-            </Label>
-            <Input
-              id="stream-smoothing-delay-ms"
-              v-model.number="systemConfig.stream_smoothing_delay_ms"
-              type="number"
-              min="1"
-              max="500"
-              placeholder="15"
-              class="mt-1"
-              :disabled="!systemConfig.stream_smoothing_enabled"
-            />
-            <p class="mt-1 text-xs text-muted-foreground">
-              每块之间的延迟毫秒数（1-500）
+            <p class="text-xs text-muted-foreground">
+              自动根据文本长度调整输出速度：短文本逐字符输出（打字感更强），长文本按块输出（避免卡顿）
             </p>
           </div>
         </div>
@@ -886,8 +838,6 @@ interface SystemConfig {
   audit_log_retention_days: number
   // 流式输出
   stream_smoothing_enabled: boolean
-  stream_smoothing_chunk_size: number
-  stream_smoothing_delay_ms: number
 }
 
 const loading = ref(false)
@@ -939,8 +889,6 @@ const systemConfig = ref<SystemConfig>({
   audit_log_retention_days: 30,
   // 流式输出
   stream_smoothing_enabled: false,
-  stream_smoothing_chunk_size: 5,
-  stream_smoothing_delay_ms: 15,
 })
 
 // 计算属性：KB 和 字节 之间的转换
@@ -999,8 +947,6 @@ async function loadSystemConfig() {
       'audit_log_retention_days',
       // 流式输出
       'stream_smoothing_enabled',
-      'stream_smoothing_chunk_size',
-      'stream_smoothing_delay_ms',
     ]
 
     for (const key of configs) {
@@ -1114,16 +1060,6 @@ async function saveSystemConfig() {
         value: systemConfig.value.stream_smoothing_enabled,
         description: '是否启用流式平滑输出'
       },
-      {
-        key: 'stream_smoothing_chunk_size',
-        value: systemConfig.value.stream_smoothing_chunk_size,
-        description: '流式平滑输出每个小块的字符数'
-      },
-      {
-        key: 'stream_smoothing_delay_ms',
-        value: systemConfig.value.stream_smoothing_delay_ms,
-        description: '流式平滑输出每个小块之间的延迟毫秒数'
-      },
     ]
 
     const promises = configItems.map(item =>