Cleanup CI warnings

Since adding the caching of nanopb logic, there is a warning if the job doesn't save to the cache.
Resolve with something like:
```
- name: Check if cache exists
id: cache-check
uses: actions/cache@v4
with:
path: ./nanopb-0.4.8.tar.gz
key: nanopb-0.4.8
enableCrossOsArchive: false

- name: Cache nanopb
if: steps.cache-check.outputs.cache-hit != 'true'
uses: actions/cache@v4
with:
path: ./nanopb-0.4.8.tar.gz
key: nanopb-0.4.8
enableCrossOsArchive: false

```

Find the GitHub Actions workflow that downloads and caches nanopb-0.4.8, then inspect the warning produced when the cache is not saved. Update the workflow so cache lookup and saving are handled without warnings, and run or inspect the affected CI job to confirm the warning is gone.

Written by the indexing model from the issue text.