[Bug]: Difference between automatic runs and manuals

### What happened?

There are some unexpected behavior of the CI checks, related to difference between automatic runs and manuals

The behavior changes depending on how are they triggered:


The last 2 runs are automatically started after a commit but the failed one started manually without any other commit on the branch.
[Automatically started job](https://github.com/insightsengineering/teal.modules.general/actions/runs/13570693514/job/37934654164) vs [Manually starting the job](https://github.com/insightsengineering/teal.modules.general/actions/runs/13584502720)

The difference is on the branch point they are, if they are [triggered automatically](https://github.com/insightsengineering/teal.modules.general/actions/runs/13570693514?pr=867), we can see:

```
No TESTING_DEPTH default.
Setting TESTING_DEPTH=5
Commit msg is: Merge 5cda9e402735617425e86521cde38c95829cc8 into 1cec0cdaae0b29ea6a0e00abc5249a4305978bd9
Check for tests/testthat/helper-TealAppDriver.R.
Run all tests: Helpers modifications detected.
At the end, using TESTING_DEPTH=5
```

[Manually](https://github.com/insightsengineering/teal.modules.general/actions/runs/13584502720/job/37976464319):

```
Run # Bash script run
No TESTING_DEPTH default.
Setting TESTING_DEPTH=5
Commit msg is: [run-all-tests]

Signed-off-by: Marcin <133694481+m7pr@users.noreply.github.com>
Error: Process completed with exit code 1.
```

This might be related to the signed-off label at the end of the commit or something else on [this line ](https://github.com/insightsengineering/r.pkg.template/blob/2e355a62625b0a63bbae51daf296b0d48ac6d378/.github/workflows/build-check-install.yaml#L559) that triggers the action to finish early with an error.

Locally the computer took ~24 minutes too, and the only modified file is a helper so no time gains are to be expected.

### sessionInfo()

```R

```

### Relevant log output

```R

```

### Code of Conduct

- [x] I agree to follow this project's Code of Conduct.

### Contribution Guidelines

- [x] I agree to follow this project's Contribution Guidelines.

### Security Policy

- [x] I agree to follow this project's Security Policy.

Start by comparing the automatically triggered and manually triggered runs linked in the issue, then inspect .github/workflows/build-check-install.yaml around line 559. Reproduce both trigger paths and determine why the manual run exits early; done means the two paths handle the test-selection logic consistently without the unexpected failure.

Written by the indexing model from the issue text.