Fix: #121 Prefer full HDF5 dataset paths as DataFrame column names

[Dhanush010]

Related Issues / Pull Requests

Follow-up to #121 (EQSIM/rechdf5 HDF5 path context)
Builds on #118 (dataset selection / no blind flatten)

Description

Prefer full HDF5 dataset paths as DataFrame column names when reading selected datasets (for example S_01_01/X instead of X).

This preserves station/group context for EQSIM-style hierarchical files so columns from different groups stay distinguishable. Valid zero fill behavior from #118 is unchanged.

What changes are proposed in this pull request?

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality not to work as expected; for instance, examples in this repository must be updated too)
• This change requires a documentation update

Checklist:

• My code modifies existing public API, or introduces new public API, and I updated or wrote documentation
• I have commented my code
• My code requires documentation updates, and I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes