feat(12-01): implement SRT parser module

- Add Segment dataclass for subtitle segments
- Add parse_srt() function to parse SRT content string
- Add parse_srt_file() function to parse from file path
- Support standard SRT format with timestamps
- Handle special characters and multi-line subtitles

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

kb_workflow/srt/__init__.py

@@ -0,0 +1,25 @@
+"""SRT Processing Module
+
+B站字幕处理模块，包含：
+- SRT 解析器 (parser)
+- 语义分段器 (segmenter)
+- ASR 纠错器 (corrector)
+"""
+
+from kb_workflow.srt.parser import parse_srt, parse_srt_file, Segment
+
+__all__ = [
+    "parse_srt",
+    "parse_srt_file",
+    "Segment",
+]
+
+# 延迟导入，避免循环依赖
+def __getattr__(name: str):
+    if name == "SemanticSegmenter":
+        from kb_workflow.srt.segmenter import SemanticSegmenter
+        return SemanticSegmenter
+    if name == "ASRCorrector":
+        from kb_workflow.srt.corrector import ASRCorrector
+        return ASRCorrector
+    raise AttributeError(f"module {__name__!r} has no attribute {name!r}")