Add J-Space Contrast Lab MVP

[arthurpanhku]

What changed

• add the Contrast Lab paired-trace research UI with aligned token streams and concept-rank trajectories
• precompute paired permutation nulls, same-language ceilings, bootstrap intervals, provenance, and answer-identity confound checks in Python
• add optional Hugging Face GPU-sidecar activation patching and Claim Card export
• add a CLI for building contrast records from existing Trace v1 pairs
• refresh deterministic demo traces and fix the audited nanoid dependency

Why

Generic J-Space viewers are useful for exploration but do not provide controlled paired evidence. This adds a small research workflow that separates visualization from statistical computation and makes claims reproducible.

Validation

• Trace gallery validation passed
• Python tests: 29 passed
• npm audit: 0 vulnerabilities
• TypeScript and Vite build passed
• browser QA at desktop and 390px responsive widths