test: cover enum, array, and JSONB columns in the sample and fixtures - #54

Summary

Extends the external sample and the PostgreSQL integration tests so that enum, array, and JSONB columns are generated, compiled, and executed end to end, including schema and query shapes modeled on sqlc's booktest example.

Changes

• The sample gains a third migration that declares a book_format enum and adds format, tags TEXT[], and details JSONB columns to books.
• Two new sample queries, CreateCatalogedBook and ListBooksByFormat, generate a shared BooksRow record and a top-level BookFormat enum; the sample application inserts a cataloged book and reads it back by format, checking the enum, the tag list, and the normalized JSONB text.
• scripts/verify-release.sh resets the enum type, applies the new migration, and expects the shared BookFormat and BooksRow files, the updated source counts and manifest, and the new repository methods.
• A new PostgreSQL integration test reproduces booktest's schema constructs with original names (serial keys, an inline reference, a unique defaulted column, an enum column with a default, timestamptz, a varchar[] column, indexes, and a dollar-quoted function) and its get, create, update, and ISBN-update query shapes, asserting the generated enum, row component types, parameter order, and round trips.

Scope and non-goals

• No compiler, runtime, or documentation changes; this adds verification only.
• booktest's title-and-year, tag-overlap, and function-call queries are not reproduced.
• The existing sample migrations and queries are unchanged.