feat(uq): add Sobol global sensitivity integration

[amaurigmartins]

Summary

• add dependency-neutral Sensitivity and SensitivityResult contracts
• integrate dependency-owned Sobol analysis through the optional GlobalSensitivity extension
• map uncertainty descriptors into physical normal or uniform coordinates
• add analytical, failure-boundary, multi-output, inference, and real cable-domain coverage
• document the public workflow and add an Ishigami reference benchmark

Validation

• full package suite: 5,516/5,516
• focused GlobalSensitivity suite: 161/161
• core-only suite: 69/69
• quality suite: 733/733
• documentation doctests: 1/1
• Ishigami benchmark: 262,144 evaluations; maximum errors below 0.00085
• core precompiles without optional dependencies
• optional extension activates with Distributions 0.25.131, GlobalSensitivity 2.12.1, and QuasiMonteCarlo 0.3.6

Review notes

This branch is based directly on release/v0.2.0. QuasiMonteCarlo's documented deterministic SobolSample()/NoRand() warning remains visible by design. The Ishigami benchmark is maintained outside CI test discovery.