Improvements

• #824 Improve settings and chat focus @zeroliu
• #843 Implement Copilot command "list indexed files" @logancyang

Bug fixes

• #842 Fix system message for non-openai models @logancyang
• #843 Alpha quick fixes @logancyang
  • Fix message edit
  • Unblock saveDB
  • Skip rerank call if max score is 0
  • Fix double indexing trigger at mode switch