Agent UI Overhaul — New Shell, Tabs & Mobile Improvements

- Redesigned agent detail page with a new tabbed shell and cleaner navigation - Template cards now show enhanced metadata and preview modals before you commit - Tools are now grouped by category with clear required/optional indicators - Tone examples and character-count guidance added to the writing style step - Agents can view and cancel their own scheduled tasks - Images sent by agents now display inline in the chat conversation - Dark mode audit — all agent creation steps now fully dark-mode compatible - Mobile keyboard and scroll behavior fixed for iOS Safari