Answer architecture round 3: New loads only sources without an index and what they read, an entry drops reads, ErrLoad sits beside New, the manifest decoder moves to manifest.go and names each mistake once as jsonvalue.Kind words it

README.md

@@ -174,13 +174,13 @@ a category may name a hidden rows file beside it.
 
 A source whose root holds `.fejkdata.json` with an `index` loads each category on the
 first call reaching it, and its author proves each loads. Any other source loads in
-`New`, and so does every indexed category that depends on what such a source provides
-or on a category a later source replaced. The index names every category of its source,
-so a category file it leaves out never loads. The shipped set's
-[`data/.fejkdata.json`](data/.fejkdata.json) shows the shape: each category's dot path,
-its `parent` table, an entry of the same index, every path `List` advertises below it,
-`""` for the category itself, and the other categories its templates `reads`. A table
-whose parent column differs from its entry's `parent` fails at first reach.
+`New`, with the indexed categories it reads. A shipped category reading one that another
+source replaced loads on its own first reach, and fails there if the replacement breaks
+it. The index names every category of its source, so a category file it leaves out never
+loads. The shipped set's [`data/.fejkdata.json`](data/.fejkdata.json) shows the shape:
+each category's dot path, its `parent` table, an entry of the same index, and every path
+`List` advertises below it, `""` for the category itself. A table whose parent column
+differs from its entry's `parent` fails at first reach.
 `//go:embed` of a directory leaves the manifest out; name it in the pattern too.
 
 Each locale carries `address`, `color`, `company`, `date`, `email`, `first-name`,