v1.13.0

Diff-based screen recording

• Record diffs between screen captures (same window + title)
• Store diff_text and diff_embedding alongside full snapshots
• search_screen_history prefers diff embeddings for better "what changed" matching
• LIKE fallback also searches diff_text

New tool: page_history

• page_history(title, minutes?, limit?) — shows initial capture + subsequent diffs for a page
• Title matched with LIKE (partial match)
• Ordered chronologically (ASC) to show evolution