fix(sawtooth): update API and regenerate references

- Update regenerate_sawtooth_refs.py to use new get_initial_state_and_post_processed_outputs API (step_fn only)
- Regenerate sawtooth_references.json with latest main branch values

Fixes failing CI tests after rebase to latest main.

Author: akshat3410

torax/_src/mhd/sawtooth/tests/regenerate_sawtooth_refs.py

@@ -164,12 +164,9 @@ def calculate_sawtooth_crash_references() -> dict[str, Any]:
       runtime_params_provider=runtime_params_provider,
   )
 
-  # Get initial state
+  # Get initial state (using new API that takes step_fn as main argument)
   initial_state, initial_post_processed_outputs = (
       initial_state_lib.get_initial_state_and_post_processed_outputs(
-          t=torax_config.numerics.t_initial,
-          runtime_params_provider=runtime_params_provider,
-          geometry_provider=geometry_provider,
           step_fn=step_fn,
       )
   )

torax/_src/mhd/sawtooth/tests/sawtooth_references.json

@@ -1,10 +1,10 @@
 {
   "post_crash_temperature": [
-    9.80214763867072,
-    9.774495567770007,
-    9.746821543811965,
-    9.719125386103409,
-    9.69140691196268,
+    9.802147638670725,
+    9.774495567770012,
+    9.746821543811969,
+    9.719125386103414,
+    9.691406911962686,
     8.179370745839305,
     6.225896595777405,
     4.499999999999998,
@@ -17,22 +17,22 @@
     9.239980390152702e+19,
     9.214698668964295e+19,
     9.189416947775886e+19,
-    8.817802446668299e+19,
-    8.345056959984748e+19,
+    8.817802446668297e+19,
+    8.345056959984746e+19,
     7.921901446691185e+19,
     7.569816937949354e+19,
     7.2177324292075225e+19
   ],
   "post_crash_psi": [
-    9.778742408396024,
-    11.342102036297204,
-    14.360383604641752,
-    18.737049105346237,
-    24.378127742662265,
-    31.058184699891584,
-    38.12617379019407,
-    44.844898859093725,
-    50.74281519306403,
+    8.245389337262555,
+    9.864264965223013,
+    12.989683251350234,
+    17.521630165994587,
+    23.36274579818155,
+    30.278108291089445,
+    37.58746532168118,
+    44.522204962167564,
+    50.597804202813315,
     55.72986584479574
   ]
 }