Test with a real GraphAr dir

[rahul21-7]

Following up on the merge in previous PR strengthened the fallback parser test to mock a real GraphAr directory structure and verify the data mapping logic.

[adsharma]

Were you able to validate the test case with any graphar tooling?

[rahul21-7]

I actually just manually constructed this as a minimal mock based on the specific fields our YamlGraphInfo fallback parser reads. Because it's minimal, it likely wouldn't pass strict validation through the official graphar tooling (it's missing fields like version, chunk_size, and property_groups).

Since we're just testing the fallback parser's mapping logic, is the minimal mock fine? Or would you prefer I pad it out with the rest of the required GraphAr schema so it's fully compliant with the official tooling?

[adsharma]

Prefer padding out since this is testing compatibility

[rahul21-7]

I padded the mock files with the required fields (version, chunk_size, property_groups, adj_lists, etc.) to match the strict GraphAr schema. I tried to validate them locally, but the official graphar python package fails to build its C++ wheels on my Windows environment. Since the fields are pulled directly from the spec, they should be fully compliant, but let me know if you spot anything I missed!

[adsharma]

Why not test with a Java version of graphar (which is hopefully better supported) or test with another database that imports graphar importing?