Article Archiving Mechanism

The program maintains a status for each article: active (currently valid) / archived (older version after the author edited it). When updating RSS:

• Compares old and new Content, archiving only triggers on body changes
• Edited articles: old version → archived, new version → active; newly added articles are written directly as active
• Deletion is no longer detected (many sites only push the latest N items in RSS; an old article disappearing doesn't mean it was deleted)