Record full JAX differential verification

README.md

@@ -143,6 +143,17 @@ CI=1 uv run pytest -q tests/lost_cities_jax/test_differential.py
 uv run pytest -q tests/lost_cities_jax/test_differential.py --full
 ```
 
+Observed differential results on 2026-07-04 with CPU JAX backend:
+
+```text
+CI=1 ... test_differential.py
+1 passed in 247.61s (0:04:07)
+
+... test_differential.py --full
+1 passed in 2514.14s (0:41:54)
+elapsed=41:54.48
+```
+
 Throughput benchmark:
 
 ```bash
@@ -155,8 +166,8 @@ Measured on 2026-07-04 with CPU JAX backend:
 backend=cpu
 batch_size=8192
 steps=256
-elapsed_sec=4.944725
-steps_per_sec=424119.01
+elapsed_sec=4.655526
+steps_per_sec=450465.14
 ```
 
 ### DECISIONS.md