fix(docs): Spanish strings were showing on the English docs

[crstian19]

The docs are English-only, but Spanish had leaked into the chrome a reader
sees. Not the prose, which is written in English: these are defaults and labels
buried in components, which is why review kept walking past them.

Showing in production right now

Where	Was
/docs/models, limits card heading	limitaciones conocidas
Every code block	Copiar, Copiado, ¡Copiado al portapapeles!, Error al copiar
Rate limits card	rate limits por API key, Paralelo máximo, concurrentes, tokens / min por modelo, requests / min por modelo

The heading came from the default title of <LimitationsCard>, used whenever
the tag carries no explicit one, so it only surfaced on the one page that omits
it.

Two places, one string

The card's default title and the rate-limit labels each live in two places
that have to agree: the component a person reads, and the extractor that
generates the text /api/docs serves to the Discord bot. Both sides are
changed together here, along with the fixture that pins the extractor's output.

That pairing is the same one rateLimits.ts exists to protect: the page and
the API had already drifted apart once over these numbers.

Guard

A test walks the docs components and the layout and fails on Spanish in
anything a reader can see. It ignores comments, since the repo deliberately
keeps Spanish ones in the layouts and styles. DocsTopBar.astro and
ApiReference.astro are exempt: their Spanish is the translated chrome of
/es/docs/api, which is the point.

It also checks that the component and the extractor agree on the default title,
rather than each being asserted in isolation.

Testing

654 tests green. The guard is verified by mutation: restoring any of the three
Spanish strings, or letting the component and the extractor drift apart, makes
the suite fail.