Add HDF5 file usage examples

[everettVT]

Summary

• Adds hdf5_func.py: demonstrates Daft's built-in HDF5 functions (hdf5_file, hdf5_attrs, hdf5_keys, hdf5_metadata) on a locally-created sample file
• Adds hdf5_udf.py: demonstrates a custom UDF that reads DROID robotics trajectory data from HDF5 files using Hdf5File and to_tempfile()

Test plan

• Run hdf5_func.py with uv run to verify sample file creation and built-in function output
• Run hdf5_udf.py with uv run to verify DROID dataset UDF extraction

🤖 Generated with Claude Code

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Declare real HDF5 dependencies

When these PEP 723 scripts are run in a fresh uv run environment, daft 0.7.16 does not provide an hdf5 extra, so this requirement does not install h5py (or numpy for hdf5_func.py). Both new scripts import h5py immediately, so the advertised self-contained examples fail with ModuleNotFoundError; please list the actual dependencies explicitly or use a published Daft extra that exists.

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[chatgpt-codex-connector]

Avoid importing unavailable HDF5 helpers

With the declared daft>=0.7.16 dependency, daft.functions does not export these HDF5 helpers, and even the current HDF5 wrapper surface does not include hdf5_attrs or hdf5_metadata. Running this example therefore fails at import time before the sample file is created; please use exported functions or wrap Hdf5File.attrs() / metadata() in UDFs.

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[chatgpt-codex-connector]

Import Hdf5File from its exported module

When this example is run with the declared Daft package, Hdf5File is not exported from the top-level daft module, so from daft import ... Hdf5File ... raises ImportError before the UDF is registered. Import it from the file module that exports it, or avoid the annotation if it is not part of the public top-level API.

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