Improved create-twenty-app documentation for AI coding agents (#20325)

Added a bit of enhanced context for better agentic coding, based on this
[Discord
conversation](https://discord.com/channels/1130383047699738754/1130383048173682821/1501538550301331477).

---------

Co-authored-by: Félix Malfait <felix@twenty.com>
Co-authored-by: Félix Malfait <felix.malfait@gmail.com>

packages/create-twenty-app/src/utils/__tests__/app-template.spec.ts

@@ -76,11 +76,16 @@ describe('copyBaseApplicationProject', () => {
       appDirectory: testAppDirectory,
     });
 
-    expect(fs.copy).toHaveBeenCalledTimes(1);
+    // Two fs.copy calls: (1) the template directory, (2) AGENTS.md → CLAUDE.md
+    expect(fs.copy).toHaveBeenCalledTimes(2);
     expect(fs.copy).toHaveBeenCalledWith(
       expect.stringContaining('template'),
       testAppDirectory,
     );
+    expect(fs.copy).toHaveBeenCalledWith(
+      join(testAppDirectory, 'AGENTS.md'),
+      join(testAppDirectory, 'CLAUDE.md'),
+    );
   });
 
   it('should replace placeholders in universal-identifiers.ts with real values', async () => {