new: scaffold materializes a schema default only for a required field

Files changed:
- CHANGES.md
- VERSION
- instructions/CONTRACT.md
- tools/CONTRACT.md
- tools/chemenu/commands/new_page.py
- tools/chemenu/tests/test_new_page.py
- types/type-spec.md

tools/CONTRACT.md

@@ -89,7 +89,7 @@ tools/wikitool <command> --help
 
 | Command | Purpose |
 |---------|---------|
-| `new <type-name> --name "<Name>" [--type <path>] [--set field=value ...]` | Scaffold a page of any type. The type-spec drives fields, defaults, directory (`base_dir`/`layout`), title prefix, and template - `--set` is repeatable, and comma-separated values fill array fields. An element that itself contains a comma is written `\,`, or passed as its own repeated `--set` for that field - repeating an array field appends. See `types list`/`types describe`. |
+| `new <type-name> --name "<Name>" [--type <path>] [--set field=value ...]` | Scaffold a page of any type. The type-spec drives fields, directory (`base_dir`/`layout`), title prefix, and template - a schema `default:` is materialized only for a field the schema also lists in `required:` (an optional field's default is a reader-side assumption, not a scaffold-time value) - `--set` is repeatable, and comma-separated values fill array fields. An element that itself contains a comma is written `\,`, or passed as its own repeated `--set` for that field - repeating an array field appends. See `types list`/`types describe`. |
 | `new entity --name "<Name>" --set entity_type=<t> [--set tags=a,b] [--set related=X,Y] [--set sources="Source - Z"] [--set provenance=sourced\|general\|mixed]` | Scaffold `kb/entities/<subdir>/<Name>.md` |
 | `new concept --name "<Name>" --set concept_type=<t> ...` | Scaffold `kb/concepts/<Name>.md` |
 | `new source --name "<Name>" --set raw_files=raw/notes/x.md,raw/notes/y.md [--set source_url=<URL>] [--set entities=A,B] [--set concepts=C,D]` | Scaffold `kb/sources/Source - <Name>.md` (prefix added automatically) with a `raw_files:` list (rejects paths that don't exist) |