gosalyn: Case 2 C2-01c brief round d2 for Webby d1: gate grep scoped to packages and docs/case2 with the six owned hits named, draft frozen with books [], hybrids may have universe-level prefixes, tests for a prefix equal to a book and for prefixes-first order (webby-0090 B1 N1 N2, mos-1240)

docs/plans/2026-10-20_case2-rows.md

@@ -1234,10 +1234,12 @@ From the ruling, which wins if this brief and it disagree:
 - `kind` is absent for a plain universe, `"hybrid"` or `"draft"`. Any other value refuses
   `library-mapping-invalid`. A draft takes only `kind`, `name` and `playground`, and needs at least one
   prefix. A draft with `books` refuses `library-mapping-invalid`. A plain universe and a hybrid keep
-  their key lists.
+  their key lists. `checkMapping` returns a draft frozen as `{kind: 'draft', name, books: [],
+  playground}`, so every reader of `books`, `classify` included (`scope.mjs:11`), gets a list.
 - Three levels, set by where a prefix sits. Book level is a prefix inside one of the entry's own book
-  folders, as now. Universe level is a prefix in a plain universe's `playground` that lies outside every
-  book folder of every entry. A draft's prefixes lie outside every book folder.
+  folders, as now. Universe level is a prefix in a plain universe's or a hybrid's `playground` that lies
+  outside every book folder of every entry. A hybrid may have `books: []` and still have universe-level
+  prefixes, and their files take the hybrid's id as `universe`. A draft's prefixes lie outside every book folder.
 - Refusals. A prefix inside, or holding, another entry's book folder refuses
   `library-playground-other-universe`. A prefix holding one of its own entry's book folders, or equal to a
   book folder, refuses `library-mapping-invalid`. The rules that no prefix holds another and none is
@@ -1256,11 +1258,15 @@ From the ruling, which wins if this brief and it disagree:
 
 Tests:
 - One case per level. A book-level file has its universe and book. A universe-level file has its
-  universe and `book: null`. A draft file has the draft's id and `book: null`. A `.canvas` under a prefix
+  universe and `book: null`, in a plain universe and in a hybrid. A draft file has the draft's id and `book: null`. A `.canvas` under a prefix
   stays `unmapped`.
 - One case per refusal: a prefix inside another entry's book, a prefix holding another entry's book, a
-  prefix holding its own book, a draft with `books`, a draft with no prefix, an unknown `kind`, a hybrid
+  prefix holding its own book, a prefix equal to a book folder (`mapping.test.mjs:20`'s `'Book One/'`
+  moves to `library-mapping-invalid`), a draft with `books`, a draft with no prefix, an unknown `kind`, a hybrid
   source naming a draft, and two overlapping prefixes in different entries.
+- A draft comes back from `checkMapping` frozen with `books: []`.
+- Prefixes first: a canon file in a book that holds a prefix, outside that prefix, stays `canon`, and a
+  file under the prefix is `playground`.
 - A reader case: a canon file linking into a draft gives R6, and linking into a universe-level prefix of
   its own universe gives R5.
 - `business.test.mjs` refuses the moved prefix with the new code through `validateBusinessDocument`.
@@ -1276,8 +1282,11 @@ verb. Hybrid `exclude` and `pin` (C2-15).
 ### Gate
 
 Webby approves the manifest. The library and business suites are green on Sage's gate, along with every
-`scripts/test-*.sh`. Grep `packages/*/tests` and `docs` for `library-playground-outside-book` before
-in-review: no hit may remain.
+`scripts/test-*.sh`. Before in-review, grep `packages` (`src`, `tests` and `README.md` files) and
+`docs/case2` for `library-playground-outside-book`: no hit may remain. At 6ba8a582e the hits are
+`mapping.mjs:84`, `packages/library/README.md:44`, `mapping.test.mjs:16-20` and `:72`,
+`business.test.mjs:25` and `SURVEY-RUN.md:114`, all owned above. The plans and `agents/` keep the old
+code as history.
 
 ### Handoffs