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

src/api/handlers/base/cli_handler_base.py

@@ -34,7 +34,9 @@ from src.api.handlers.base.base_handler import (
 from src.api.handlers.base.parsers import get_parser_for_format
 from src.api.handlers.base.request_builder import PassthroughRequestBuilder
 from src.api.handlers.base.stream_context import StreamContext
+from src.api.handlers.base.stream_processor import create_smoothed_stream
 from src.api.handlers.base.utils import build_sse_headers
+from src.services.system.config import SystemConfigService
 
 # 直接从具体模块导入，避免循环依赖
 from src.api.handlers.base.response_parser import (
@@ -352,8 +354,17 @@ class CliMessageHandlerBase(BaseMessageHandler):
             # 创建监控流
             monitored_stream = self._create_monitored_stream(ctx, stream_generator)
 
+            # 创建平滑输出流（如果启用）
+            smoothing_enabled = bool(
+                SystemConfigService.get_config(self.db, "stream_smoothing_enabled", False)
+            )
+            if smoothing_enabled:
+                final_stream = create_smoothed_stream(monitored_stream)
+            else:
+                final_stream = monitored_stream
+
             return StreamingResponse(
-                monitored_stream,
+                final_stream,
                 media_type="text/event-stream",
                 headers=build_sse_headers(),
                 background=background_tasks,