[dajiaohuang]

Summary

• Preserve an explicit stop=0 in ggml.utils.slice_tensor; slice(0, 0) now requests a zero-length view instead of the full axis.
• Add a focused regression test with a synthetic ggml API fixture, so the Python wrapper can be tested without a native build.
• Add the required Unreleased changelog entry.

Verification

• The regression failed before the fix (view API received (4, 0)) and passes after it ((0, 0)). Local command: PYTEST_DISABLE_PLUGIN_AUTOLOAD=1 py -3.13 -B -m pytest -q tests/test_slice_tensor_empty.py — 1 passed.
• ruff check --no-cache ggml tests and ruff format --check --no-cache --exclude ggml/ggml.py ggml tests pass.
• The full native suite/build was not run locally; CMake/compiler are unavailable in PATH. No model assets, inference, or external AI service were used.