Fix pytest baseline geometry, NOBE, and NumPy issues

[eggpig]

Summary

• make common_tangent_radian raise ValueError for invalid circle geometry instead of silently clamping impossible inputs
• make NOBE_SH and NOBE_GA_SH reject empty graphs before indexing empty embedding results
• make GraphML/GEXF NumPy type mapping compatible with NumPy 2.x, where np.float_ has been removed
• update the GraphML NumPy float test to use the same compatibility pattern

Semantics

• The geometry change only rejects cases where the distance is non-positive or too small for the requested tangent calculation, plus negative radii.
• The NOBE change keeps the existing invalid K and topk behavior and adds an explicit empty-graph error.
• The NumPy change keeps np.float64, np.float32, and np.float16 mappings unchanged, and falls back to np.float64 when np.float_ does not exist.

Verification

• git diff --check
• black --check and isort --check-only on changed files
• focused pytest for geometry, NOBE, GEXF, and GraphML: 62 passed, 20 skipped without lxml
• after installing lxml, GEXF/GraphML tests: 56 passed
• manual checks for:
  • valid and invalid common_tangent_radian inputs
  • empty graph errors for NOBE_SH and NOBE_GA_SH
  • karate graph NOBE smoke checks
  • GraphML/GEXF writing with np.float64 on NumPy 2.0

Note

A local full pytest easygraph run was started but did not complete in a reasonable time on my machine, so I terminated it and relied on focused tests plus GitHub Actions for full-suite validation.