A project's locale list silently accrues whoever opens it

[amyjko]

Project.deserialize unions the project's declared locales with the viewer's currently selected UI locales (Project.ts#L1229-L1236), and serialize() writes that merged list back (Project.ts#L1466):

const dependentLocales = await localesDB.loadLocales(
    getBestSupportedLocales(project.locales),
);
const locales = Array.from(
    new Set([...dependentLocales, ...localesDB.getLocales()]),
);

LocalesDatabase.setLocales → Projects.localize → Project.withLocales additionally prepends newly chosen locales to every tracked project, so switching UI language once rewrites the locale list of every open project. Nothing ever removes a locale, so a project only gains them, and its Basis — hence the names bound in scope — depends on who last opened it.

This is how #1228 reproduced on a personal copy but not the gallery copy of the same program: examples recompute locales from their === name/lang source headers (examples.ts#L86) and stayed single-locale, while the persisted personal copy had accrued hi-IN.

Two smaller things in the same area:

• A locale whose fetch fails at load time is silently dropped from the in-memory list, and the next save then drops it from the stored project.
• Project.getLocalesUsed() — the set actually derived from the code — never feeds the persisted locales field.

Not a correctness bug on its own (multi-locale projects have to work regardless, which is what #1228 fixed), but the accrual makes a project's analysis depend on its viewer, which is surprising and made that bug hard to reproduce.