fix for potential errors in z_cor_test

[arcaldwell49]

Code failed when 1) NAs present in one vector 2) correlation is perfect but jackknife se selected. Pull fixes the code and puts in unit tests to avoid future error in same fashion.

[Copilot]

Pull request overview

This PR addresses failure cases in z_cor_test() by making correlation tests robust to missing paired values and by preventing the jackknife SE path from producing invalid results when Fisher’s z-transform becomes infinite (|r| = 1). It also adds regression tests to prevent these error modes from returning.

Changes:

• Filter to complete paired observations before computing cor()/SEs in z_cor_test().
• Add explicit guards/errors for jackknife SE when |r| = 1 (or when the computed SE is non-finite/zero).
• Add unit tests covering NA handling and the |r| = 1 jackknife failure mode.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.

File	Description
R/cor_test.R	Updates z_cor_test() to drop NA pairs before correlation/SE computation and adds jackknife SE guards.
tests/testthat/test-corr.R	Adds regression tests for NA handling and perfect-correlation jackknife errors.
.claude/settings.local.json	Unrelated local settings changes included in the PR (should be removed).