Make robust to lack of pytest log

[ianhi]

Sometimes a scheduled test run fails before we even reach pytest. e.g. due to dependency resoltion issues introduced by upstream factors. This results in teh workflow failing and not making an issue, which results in it sneaking through. See here: https://github.com/earth-mover/icechunk/actions/runs/19555246916/job/55996098343

Run python $GITHUB_ACTION_PATH/parse_logs.py icechunk-python/output-pytest-log.jsonl
Parsing logs ...
Traceback (most recent call last):
  File "/home/runner/work/_actions/xarray-contrib/issue-from-pytest-log/v1/parse_logs.py", line 229, in <module>
    lines = args.filepath.read_text().splitlines()
            ~~~~~~~~~~~~~~~~~~~~~~~^^
  File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/pathlib/__init__.py", line 792, in read_text
    with self.open(mode='r', encoding=encoding, errors=errors, newline=newline) as f:
         ~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/hostedtoolcache/Python/3.14.0/x64/lib/python3.14/pathlib/__init__.py", line 776, in open
    return io.open(self, mode, buffering, encoding, errors, newline)
           ~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: 'icechunk-python/output-pytest-log.jsonl'
Error: Process completed with exit code 1.

[ianhi]

Or alternatively, we should add an action step for reporting errors from an install step like i do here: earth-mover/icechunk@d69a991