feat(core): name every show by its row id

[noctuum]

A show is named by ShowId, the id of its row in shows, through recognition, the session and the store. A title is what a person is shown, and AniList holds entries that share one: four romaji titles of the five thousand most popular entries belong to two entries each. Filed by title, two such entries merged into one.

• Corpus::file takes the show. A Match carries it beside the title, and an Ambiguity lists Candidates that do. The index and the scorer work on shows, and an Assignment names one.
• The session's effects name the show, and a sitting is told apart by show and episode.
• Migration 2 rebuilds shows without the uniqueness of its title, since ALTER TABLE in SQLite cannot drop a constraint. Migrations run with the foreign keys off and set them back as found: the pragma does nothing inside a transaction, and dropping a table that rows of other tables point at is refused while they are on.
• Store::new_show files a show. record, keep, resume and close take a ShowId and file nothing, and an Operation carries its show.

Over names built from those five thousand entries, 4,425 a form in seven forms, one name a form moved from answered to refused: a spelling that a series and its special share under one title. Every other answer is the same.

cargo test --workspace passes, 822 tests.