Give Gemini Code a face lift.

- This utilizes `ink-gradient` to render GEMINI CODE in amazing colors.
- Added a shared color configuration for UX (should this be in config?). It's very possible that we shouldn't be talking about the specific colors and instead be mentioning "foreground"/"background"/inlineCode etc. type colors.
- Updated existing color usages to utilize `Colors.*`

Fixes https://b.corp.google.com/issues/411385593

packages/cli/src/ui/components/messages/ToolConfirmationMessage.tsx

@@ -16,6 +16,7 @@ import {
 import { PartListUnion } from '@google/genai';
 import { DiffRenderer } from './DiffRenderer.js';
 import { UI_WIDTH } from '../../constants.js';
+import { Colors } from '../../colors.js';
 
 export interface ToolConfirmationMessageProps {
   confirmationDetails: ToolCallConfirmationDetails;
@@ -74,7 +75,9 @@ export const ToolConfirmationMessage: React.FC<
       confirmationDetails as ToolExecuteConfirmationDetails;
 
     // For execution, we still need context display and description
-    const commandDisplay = <Text color="cyan">{executionProps.command}</Text>;
+    const commandDisplay = (
+      <Text color={Colors.AccentCyan}>{executionProps.command}</Text>
+    );
 
     // Combine command and description into bodyContent for layout consistency
     bodyContent = (