Add builder generation trace metadata

seed_config.py

@@ -216,3 +216,24 @@ def axis_rng(seed_config: dict[str, int], axis: str, base_seed: int, row_number:
     if configured is None:
         return random.Random(row_seed(base_seed, row_number, salt))
     return random.Random(row_seed(configured, row_number, salt))
+
+
+def axis_seed_trace(
+    seed_config: str | dict[str, Any] | None,
+    base_seed: int,
+    row_number: int,
+    axes: Iterable[str] = SEED_LOCK_AXES,
+) -> dict[str, dict[str, int | str]]:
+    parsed = parse_seed_config(seed_config)
+    trace: dict[str, dict[str, int | str]] = {}
+    for axis in axes:
+        configured = configured_axis_seed(parsed, axis)
+        seed_value = int(configured) if configured is not None else int(base_seed)
+        source = "configured" if configured is not None else "main"
+        salt = SEED_AXIS_SALTS.get(axis, 0)
+        trace[axis] = {
+            "source": source,
+            "seed": seed_value,
+            "rng_seed": row_seed(seed_value, row_number, salt),
+        }
+    return trace