ECL, default scale, and preferred alignment entries

README.md

@@ -268,8 +268,21 @@ autogen:
 `topdata.value_encodings` enables configured authoring sugar for compact 2DA
 cell values. The `packed_hex_list` mode accepts authored values such as
 `{"list": [0, {"range": [10, 12]}]}` and emits a single `0x...` string with
+fixed-width hex chunks. The `alignment_hex_list` mode accepts two-letter
+alignment codes such as `{"list": ["le", "CG"]}` and emits the corresponding
 fixed-width hex chunks.
 
+`topdata.value_defaults` applies configured fallback values to missing or
+null-like cells before 2DA emission:
+
+```yaml
+topdata:
+  value_defaults:
+    - dataset: racialtypes/core
+      column: ECL
+      value: 0
+```
+
 `paths.source` and `paths.assets` must name real repository subtrees when they
 are configured. They may be omitted for repositories that do not own that class
 of source, but they must not resolve to the repository root (`.`). Output and