style(vscode-ide-companion): update UI components and styling

- Updated chat message container spacing and styling
- Adjusted AssistantMessage text color handling
- Enhanced QwenMessageTimeline CSS rules for better visual flow
- Moved InfoBanner to ui directory for better organization
- Updated InputForm styling
- Added new CSS classes and updated tailwind configuration
- Improved timeline connection lines and message item spacing

These changes enhance the visual appearance and user experience of the chat interface.

packages/vscode-ide-companion/src/webview/components/InputForm.tsx

@@ -201,6 +201,9 @@ export const InputForm: React.FC<InputFormProps> = ({
               </button>
             )}
 
+            {/* Spacer */}
+            <div className="flex-1 min-w-0" />
+
             {/* Thinking button */}
             <button
               type="button"