[dajiaohuang]

Problem

Several usage-guide instructions no longer match the public API on main:

• The points examples load a nonexistent test/data/filters/filters.ply, and pandas.tools.plotting no longer imports.
• get_k_neighbors, points_random_sampling/mesh_random_sampling, abbreviated inclination/orientation names and ommnivariance do not resolve to the current public methods/registries.
• Voxel scalar fields/samplers require voxelgrid_id; KDTree filters require kdtree_id. Following the listed old keyword names raises TypeError.
• The mesh export example passes the removed internal argument instead of also_save; .npy is not a registered file format.
• Several autoclass names are stale or refer to the wrong class.
• Python prerequisites differ from pyproject.toml (>=3.11), and one combined pytest invocation collides on repeated unit/integration module names. CI already runs the two suites separately.

Changes

Correct those existing instructions and references, make the six-point points example self-contained, and synchronize the affected generated public API notes (voxelgrid arguments/defaults, sampler/filter identifiers and DataFrame sample return). No runtime behavior, dependency requirements or public interfaces change.

Validation

Windows / Python 3.12.13 / NumPy 2.2.6 / pandas 2.2.3 / SciPy 1.15.3:

• A local documentation-contract harness reproduces 13 failing instruction/reference groups on 8368c6a and passes all 13 after correction. Checks include executing the points example, importing scatter_matrix, actual public API calls with the documented identifiers, mesh OBJ export/reload, format/registry membership and package-metadata prerequisites.
• Four additional API-note comparisons now match the real constructor signatures/return contract. The executable AST of core_class.py is unchanged after removing docstrings.
• The README PLY → HSV → voxelgrid → nearest sampling → NPZ example runs on a generated six-point cloud. Corrected pandas box/scatter plots run with Matplotlib Agg; no interactive notebook/widget-rendering claim.
• python -m sphinx -E -b html docs <temporary-output> succeeds with seven existing config/developer-reference warnings outside the corrected references. This is not a warning-free whole-documentation claim.
• Ruff 0.9.10 lint/format checks pass for the Python docstring change; git diff --check passes. Repository-wide flake8 and codespell still find existing issues (including unchanged trough in these guides). Broader runtime test limitations are unchanged from base; this is documentation-only.

This does not duplicate #363's PCD URL/writer changes, and does not modify deprecated notebooks in the separate pyntcloud-notebooks repository.