bug: browser tests risk orphaned resources.

https://github.com/aws/agentcore-cli/issues/1493 also applies to browser tests.

We should be able to re-use the same solution by refactoring browser tests to live within e2e tests, or creating a new top-level tests directory, and putting the shared utils in there.

Ex.
```
tests/
e2e-tests/
integ-tests/
browser-tests/
utils/
```

or something like

```
e2e-tests/
browser/
utils/
cli/
```