cli: `cdk bootstrap` using temporary credentials (session) fails to create resources in CloudFormation stack

### Describe the bug

The CloudFormation stack created via `cdk bootstrap` fails to create any resources when run using temporary credentials via was-vault. It fails with the error:

```
The security token included in the request is invalid
```

### Regression Issue

- [ ] Select this option if this issue appears to be a regression.

### Last Known Working CDK Library Version

_No response_

### Expected Behavior

Bootstrap successfully runs using the temporary credentials.

### Current Behavior

Bootstrap creates the CloudFormation stack but fails to create the resources. It then fails to rollback due to the same permissions error.

### Reproduction Steps

1. Init a new project with `cdk init app --language typescript`
2. Update stack to set the right account ID and region
3. Run `was-vault exec -- npx cdk bootstrap`

### Possible Solution

_No response_

### Additional Information/Context

I was trying to bootstrap my account using the `cdk bootstrap` command using [aws-vault](https://github.com/99designs/aws-vault) for authentication. This creates a session which is passed through to the subprocess via the environment variables:

- `AWS_ACCESS_KEY_ID`
- `AWS_SECRET_ACCESS_KEY`
- `AWS_SESSION_TOKEN`

When I ran the bootstrap just using my long lived access key (via the `--no-session` flag on was-vault), the CloudFormation stack was able to successfully create all the resources.

### AWS CDK Library version (aws-cdk-lib)

2.206.0

### AWS CDK CLI version

2.1023.0 (build 45ceb89)

### Node.js Version

v24.4.1

### OS

MacOS

### Language

TypeScript

### Language Version

_No response_

### Other information

_No response_

Start by reproducing `cdk bootstrap` from the reported TypeScript project with `AWS_ACCESS_KEY_ID`, `AWS_SECRET_ACCESS_KEY`, and `AWS_SESSION_TOKEN`, then compare it with the `--no-session` case. Trace the `cdk bootstrap` entry point through CloudFormation resource creation and rollback; done means temporary credentials allow all resources to be created and the stack to roll back successfully on failure.

Written by the indexing model from the issue text.