fix(gh): don't early exit on failure for "pr checks"

if there are failing checks in the PR, then `gh` will return a status of
`1` and `rtk` will refuse to parse the output due to using
`early_exit_on_failure`.

remove the use of `early_exit_on_failure` so it can still parse the
output.

now if there is an error, we will still get the summarised output with
all `0`s, and we'll also pass through the stderr.

example if a repository does not exist:

```
CI Checks Summary:
  [ok] Passed: 0
  [FAIL] Failed: 0
GraphQL: Could not resolve to a Repository with the name 'some-org/some-repo'. (repository)
```

with the error passed through to the output regardless, the error
handling downstream by the LLM should still work well.