feat(05-02): implement ArchiveProcessor

- Create ArchiveProcessor with STEP_NAME = archive
- Implement process() method with idempotent execution
- Add _find_existing_archive() for duplicate detection
- Add _ask_overwrite() using rich.prompt with fallback
- Only copy md files (not json) to archive directory
- Export ArchiveProcessor in __init__.py

kb_pipeline/processors/__init__.py

@@ -6,6 +6,7 @@ This module contains processors for various content transformation tasks:
 - DownloadProcessor: Metadata and content downloading
 - ASRProcessor: Audio-to-text conversion (subtitle download + Whisper.cpp)
 - AnalyzeProcessor: AI-powered content analysis using DeepAnalyzer
+- ArchiveProcessor: Copy analysis reports to archive directory
 """
 
 from .base import BaseProcessor
@@ -13,5 +14,13 @@ from .parse import ParseProcessor
 from .download import DownloadProcessor
 from .asr import ASRProcessor
 from .analyze import AnalyzeProcessor
+from .archive import ArchiveProcessor
 
-__all__ = ["BaseProcessor", "ParseProcessor", "DownloadProcessor", "ASRProcessor", "AnalyzeProcessor"]
+__all__ = [
+    "BaseProcessor",
+    "ParseProcessor",
+    "DownloadProcessor",
+    "ASRProcessor",
+    "AnalyzeProcessor",
+    "ArchiveProcessor",
+]