Profiler: surface chi-squared proxy hints between detected columns

[yakew7]

Summary

faircode/SPEC.md §3 notes an optional scipy.stats.chi2_contingency proxy check that is not wired into the output. Add an opt-in pass that flags pairs of columns that are strongly associated (a "this column may be a proxy for that protected attribute" hint).

Why

Bridges the Profiler (representation) to the audits (proxy removal) — the same chi-squared pattern already used across the audit scripts.

Tasks

• CLI --proxy-hints flag (scipy optional dependency)
• Report flagged pairs with p-values
• Note in SPEC.md that this is informational, not scored