Tier I: SST patch experiments — East vs West Pacific causal response

## Description
Test causal interactions by comparing responses to localized SST warming in the Eastern vs Western Tropical Pacific.

## Specification
- Two paired AMIP-style experiments with localized SST perturbations
- Evaluate whether model produces qualitatively different responses in the two regions (as expected on physical grounds)
- Compare against Williams et al. (2023) and GFMIP results

## Required variables
`tas`, `pr`, `rlut`, `rsut`, `psl`

## Required simulations
SST patch (East Pacific), SST patch (West Pacific)

## References
Williams et al., 2023; GFMIP protocol