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/Tips.tsx

@@ -6,19 +6,28 @@
 
 import React from 'react';
 import { Box, Text } from 'ink';
-import { UI_WIDTH } from '../constants.js';
+import { Colors } from '../colors.js';
 
 export const Tips: React.FC = () => (
-  <Box flexDirection="column" marginBottom={1} width={UI_WIDTH}>
-    <Text>Tips for getting started:</Text>
-    <Text>
-      1. <Text bold>/help</Text> for more information.
+  <Box flexDirection="column" marginBottom={1}>
+    <Text color={Colors.Foreground}>Tips for getting started:</Text>
+    <Text color={Colors.Foreground}>
+      1.{' '}
+      <Text bold color={Colors.AccentPurple}>
+        /help
+      </Text>{' '}
+      for more information.
     </Text>
-    <Text>
-      2. <Text bold>/init</Text> to create a GEMINI.md for instructions &
-      context.
+    <Text color={Colors.Foreground}>
+      2.{' '}
+      <Text bold color={Colors.AccentPurple}>
+        /init
+      </Text>{' '}
+      to create a GEMINI.md for instructions & context.
     </Text>
-    <Text>3. Ask coding questions, edit code or run commands.</Text>
-    <Text>4. Be specific for the best results.</Text>
+    <Text color={Colors.Foreground}>
+      3. Ask coding questions, edit code or run commands.
+    </Text>
+    <Text color={Colors.Foreground}>4. Be specific for the best results.</Text>
   </Box>
 );