Refactor: Remove GEMINI.md memory and refactor system prompt

- Updates CONTRIBUTING.md and Tips.tsx to remove references to GEMINI.md and the /init command, and renumbers tips.
- Fixes a typo in Tips.tsx ("information.s" -> "information.").
- Refactors the core system prompt in prompts.ts from a constant string to a function .
- Updates client.ts to call the  function.
- Updates tool name references within the system prompt to use template literals for dynamic naming.

Fixes bug: https://buganizer.corp.google.com/issues/413061073
---

Generated by yours truly __Gemini Code__

packages/cli/src/ui/components/Tips.tsx

@@ -19,15 +19,8 @@ export const Tips: React.FC = () => (
       for more information.
     </Text>
     <Text color={Colors.Foreground}>
-      2.{' '}
-      <Text bold color={Colors.AccentPurple}>
-        /init
-      </Text>{' '}
-      to create a GEMINI.md for instructions & context.
+      2. Ask coding questions, edit code or run commands.
     </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>
+    <Text color={Colors.Foreground}>3. Be specific for the best results.</Text>
   </Box>
 );