vX.Y.Z: finalize data sampling compatibility surface

Highlights

This release expands the data loading, transform, dataset, and compatibility surface across vgl, with a focus on smoother migration from legacy imports and broader coverage for practical graph training
workflows.

• Added broader advanced dataloading support, including random-walk, Node2Vec, GraphSAINT, Cluster-GCN, and ShaDow-style sampling surfaces.
• Added public dataset coverage and example modules for Planetoid, TU datasets, GraphSAINT, and Cluster-GCN style workflows.
• Split and expanded transform exports into clearer public modules, including base, compose, feature, split, and structure-oriented transforms.
• Extended legacy compatibility shims for vgl.data, vgl.data.sampler, vgl.data.transform, vgl.data.plan, vgl.data.executor, vgl.data.requests, and vgl.data.materialize.
• Extended representative compatibility re-exports for legacy vgl.train and vgl.core import paths.
• Improved link prediction compatibility around query ids, negative sampling behavior, and related loader/split coverage.
• Improved docs and README guidance for preferred imports, compatibility imports, testing, and local release verification.

Compatibility

For new code, prefer importing from the domain packages directly:

• vgl.graph
• vgl.dataloading
• vgl.transforms
• vgl.engine

Legacy import paths remain available as compatibility shims to help existing projects migrate incrementally:

• vgl.core
• vgl.data
• vgl.data.sampler
• vgl.data.transform
• vgl.data.plan
• vgl.data.executor
• vgl.train

Included Examples

This release adds or strengthens example coverage for:

• Planetoid node classification
• TU graph classification
• GraphSAINT node classification
• Cluster-GCN node classification

Verification

Validated locally with:

• python -m pytest -q -> 1118 passed, 2 warnings
• python scripts/public_surface_scan.py -> 84/84 passed
• python scripts/full_scan.py -> 100/100 passed
• python scripts/docs_link_scan.py -> 11/11 passed