Resolves #691

Overview

Fixes that sometimes synonym_sync_combined_cases.robot.tsv would be empty.
Also fixes: Sometimes builds would pause in a particular place until some input was made in the terminal.

Additional info

Cause:
I was just about to start working on #691 when I asked Claude about why my builds were pausing; turns out these are related!

for file in ; do \
  tail -n +3 $file >> reports/sync-synonym/synonym_sync_combined_cases.robot.tsv; \
done

There's no list of files after for file in - it's empty. This means the loop will execute zero times, but it still needs to be processed by the shell.
The head -n 2 command appears to be dangling without an input:
head -n 2 > reports/sync-synonym/synonym_sync_combined_cases.robot.tsv
It's waiting for input from stdin, which would cause it to pause until it receives input (or you press Ctrl+D to signal EOF).

This explains why this happened to me usually, Nico sometimes, and Trish never. This doesn't happen unless you run a build on a fresh clone!

Additional tweaks made:
The "combined cases" file has become a permanent curation file. It made sense to formalize it as such in this PR. Formalizing it this way also made the bug fix easier to implement.

Pre-merge checklist

Documentation

Was the documentation added/updated under docs/?

• Yes
• No, updates to the docs were not necessary after careful consideration

QC

Was the full pipeline run before submitting this PR using sh run.sh make build-mondo-ingest on this branch (after
docker pull obolibrary/odkfull:dev), and no errors occurred?

• Yes
• No, there are no functional (code-related) changes to the pipeline in the PR, so no re-run is necessary

Build:

• DO NOT MERGE: Bug fixes: Synonym Sync - combined cases - build #730

New Packages

Were any new Python packages added?

• Yes, requirements.txt.full was updated and an ODK issue submitted
• No

Were any other non-Python packages added?

• Yes, Dockerfile updated and an ODK issue submitted
• No

PR Review and Conversations Resolved

Has the PR been sufficiently reviewed by at least 1 team member of the Mondo Technical team and all threads resolved?

• Yes