Refine CI install and test checks

[eggpig]

Summary

• run the existing EasyGraph pytest suite only for pull requests and pushes targeting pybind11
• make the cross-platform PR code review job validate pip install plus a minimal EasyGraph graph smoke test
• replace the broken python tests/test.py command, since tests/test.py does not exist
• make the CMake/pybind11 build use the active Python interpreter so pip install produces a usable cpp_easygraph extension for that Python version
• run pre-commit only on changed files in CI, so historical formatting debt no longer blocks unrelated PRs
• update checkout/setup-python actions in the affected workflows

Test layout notes

• The main EasyGraph pytest suite currently has 87 Python test files under easygraph.
• pytest.ini collects **/tests/test_.py, so the C++ community cpp__test.py files are not part of the main pytest run.
• The cpp_easygraph/pybind11/tests tree belongs to the pybind11 submodule and should not be mixed into EasyGraph's normal CI.

Verification

• YAML parsed successfully for .github/workflows/test.yaml, .github/workflows/pr_code_check.yaml, and .github/workflows/pre-commit.yaml
• git diff --check
• clean worktree with submodules: pip install requirements, pip install EasyGraph, then import EasyGraph from /tmp and build a minimal graph
• verified the installed extension uses the active Python ABI tag: cpp_easygraph.cpython-39-darwin.so in the local Python 3.9 venv

Follow-up

This PR fixes CI structure, the broken cross-platform test command, the pre-commit all-files blocker, and a pip install/import packaging issue exposed by the new smoke test. The full pytest workflow can only turn green after the current baseline pytest failures are resolved.

[eggpig]

Latest CI status after the workflow updates:

• pre-commit now passes with changed-files checking.
• PR code review build/install/smoke passes on all six platform/Python jobs:
  • Windows 3.9 / 3.12
  • macOS 3.9 / 3.12
  • Ubuntu 3.9 / 3.12
• Full pytest is now running and failing on real baseline test failures, not on the old missing tests/test.py workflow error.

Current pytest failure groups:

1. easygraph/functions/drawing/tests/test_geometry.py::TestGeometryUtils::test_common_tangent_radian_invalid

   • common_tangent_radian(5, 1, 2) does not raise ValueError.

2. easygraph/functions/structural_holes/tests/test_NOBE.py empty-graph cases

   • NOBE_SH / NOBE_GA_SH index into an empty embedding result before raising the expected ValueError.

3. easygraph/readwrite/tests/test_gexf.py and easygraph/readwrite/tests/test_graphml.py

   • NumPy 2.0 removed np.float_; readwrite type mapping still references np.float_.

4. easygraph/tests/test_hif.py::HIFTest::test_hif_roundtrip_preservation

   • hif_to_hypergraph currently stores attrs['name'] such as Node A / Node B as v_property name, while the test expects HIF node IDs n1 / n2.

I am leaving these as follow-up product/test fixes rather than mixing them into this CI workflow PR, because they touch multiple EasyGraph functional areas.