Deployment fails since update

### How did you install the Amplify CLI?

Amplify Console is in use

### If applicable, what version of Node.js are you using?

_No response_

### Amplify CLI Version

latest from the console

### What operating system are you using?

Amplify CLI with a Flutter web app

### Did you make any manual changes to the cloud resources managed by Amplify? Please describe the changes made.

-

### Describe the bug

Since a few days, in the console the deployment is failing due to submodules:
```
13

2025-07-08T04:26:23.614Z [INFO]: Successfully cleaned up Git credentials

14

2025-07-08T04:26:23.614Z [INFO]: # Checking for Git submodules at: /codebuild/output/src1568553444/src/repository_name/.gitmodules

15

2025-07-08T04:26:23.615Z [INFO]: # Updating Git submodules...
2025-07-08T04:26:24.005Z [WARNING]: # Unable to update submodules: Error: Command failed: git submodule update

17

Cloning into '/codebuild/output/src1568554444/src/repository_name/backend'...

18

fatal: could not read Username for 'https://github.com': No such device or address

19

fatal: clone of 'https://github.com/company-org/backend.git' into submodule path '/codebuild/output/src1568553302/src/repository_name/backend' failed

20

Failed to clone 'backend'. Retry scheduled

21

Cloning into '/codebuild/output/src1568554444/src/repository_name/lib/core_lib'...

22

fatal: could not read Username for 'https://github.com': No such device or address

23

fatal: clone of 'https://github.com/companyorg/core_lib.git' into submodule path '/codebuild/output/src1568554444src/repository_name/lib/core_lib' failed

24

Failed to clone 'lib/core_lib'. Retry scheduled

25

Cloning into '/codebuild/output/src1568553302/src/repository_name/backend'...

26

fatal: could not read Username for 'https://github.com': No such device or address

27

fatal: clone of 'https://github.com/company-org/backend.git' into submodule path '/codebuild/output/src15685534444/src/repository_name/backend' failed

28

Failed to clone 'backend' a second time, aborting

29

2025-07-08T04:26:24.022Z [INFO]: # Retrieving environment cache...
``

### Expected behavior

Deploy the app

### Reproduction steps

Deploy with submodules to Amplify a web app

### Project Identifier

_No response_

### Log output

```
# Put your logs below this line

```

### Additional information

_No response_

### Before submitting, please confirm:

- [x] I have done my best to include a minimal, self-contained set of instructions for consistently reproducing the issue.
- [x] I have removed any sensitive information from my code snippets and submission.

The deployment log and repository .gitmodules are the named investigation points; start by checking how Amplify Console retrieves the private GitHub submodules. Confirm the authentication failure with the listed submodules, then verify that deployment completes without the git submodule username error.

Written by the indexing model from the issue text.