Add permutation-column VIP / CV-beta null for the observational relate

[kgdunn]

Summary

• In the p >> n observational relate, even a descriptor with no real relationship earns a non-trivial VIP, so a driver-magnitude threshold cannot come from the fit alone. New process_improve.sensory.permutation_column_null builds one from the data itself.
• It appends permuted knockoff columns - each a row-shuffled copy of a real descriptor, preserving that column's own marginal (spread, sparsity, support) rather than simulating a distribution - refits the PLS relate over n_iter permutations, and reports, per surviving descriptor, whether its VIP and cross-validated beta clear a high quantile of the knockoff null band (vip_exceeds_null / cv_beta_exceeds_null).
• Decoupled from the influence gate. It takes an ignore list of descriptor names (validated - an unknown name raises, so a typo fails loudly) that are dropped from the fit entirely, not merely skipped when building knockoffs, so a caller passes the gate-demoted spikes and calibrates only the survivors, undistorted. The knockoff count scales with the block (fraction, a min_knockoffs floor for narrow data, optional cap); n_iter is the permutation count.
• No simulation: the null is permutations of the real chemistry values. Deterministic given random_state.

Test plan

• uv run pytest tests/test_sensory.py --no-cov (53 passed). New tests: genuine drivers clear the null while noise columns fall below them; ignore drops named columns from the fit and output; an unknown ignore name raises; identical output for a fixed seed; out-of-range fraction / quantile are rejected.
• Exercised on the real sparse strawberry data during development: with the gate-demoted spikes passed as ignore, the surviving well-supported chemicals are calibrated against their own permuted-column null.
• uv run ruff check . and uv run mypy src/process_improve pass.

Checklist

• Version bumped in pyproject.toml (MINOR: 1.57.0 -> 1.58.0, new public API; CITATION.cff synced)
• Tests added or updated where relevant
• ruff check . passes
• CHANGELOG.md updated

🤖 Generated with Claude Code

https://claude.ai/code/session_018M9u5EpSjHa3mjNaYDJ7qq

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