ChatDigi AI 4.2.6 - Mobile Chat First

Changes:
- Single chat pages on mobile now prioritize the active conversation instead of admin page information.
- Automatically scrolls mobile users directly to the live chat panel.
- Compresses the AI Chat Center heading on mobile single-chat view.
- Hides noisy WordPress/admin notices on the chat page on mobile.
- Keeps visitor status, focus status, and action buttons in a compact top operator bar.
- Makes the message list taller and the reply composer sticky at the bottom.
- Reduces mobile button/input spacing for faster real phone chatting.
