Refactor: Improve chat input UI and suggest performance enhancements.

[rkarahan80]

UI Change (webui/index.html, webui/index.css):

• Restructured the text button row in the chat input area.
• Kept "Pause/Resume Agent" and "Files" buttons visible.
• Moved "Import Knowledge", "History", "Context", and "Nudge" buttons into a new "More Actions" dropdown menu.
• This declutters the input area while keeping all actions accessible.
• Added CSS for the dropdown and ensured responsiveness.

Performance Recommendations (Conceptual):

• Frontend: Suggested bundling/minifying CSS & JS assets, optimizing images, and reviewing script loading strategies (defer/async).
• Backend (agent.py): Suggested implementing caching for prompts/tools/extensions, reviewing history management for scalability, auditing custom tools/extensions for non-blocking async operations, and using profiling tools for future bottleneck identification.