Extended Thinking Display Enhancements

What: Improved visual presentation of thinking blocks with collapsible display option.

Details:

• New "∴" (therefore) symbol for extended thinking display
• Collapsed view shows "∴ Thinking (ctrl+o to expand)" hint
• Expanded view shows "∴ Thinking…" with full content
• Smart filtering excludes tool result messages from thinking analysis
• Evidence: Display logic in BYB() at line 414832, message filter FYB() at line 415832