Documentation: Core input prefixes (!, @) buried in slash-commands page

Key points to highlight:

• Basic input prefixes (!, @) are essential daily-use features
• Currently buried in "slash-commands" (perceived as advanced)
• Should be prominently featured in "Interactive Mode" or "Quick Start"
• Creates unnecessary friction for new users
• Forces users to Google basic functionality

Suggested reorganization:

• Move core input patterns to Interactive Mode page
• Update Quick Start to mention !command and @file syntax
• Reserve slash-commands page for custom command creation