Paginate Google model refresh

[thossullivan]

What changed

• follows Google models.list nextPageToken values until the terminal page
• requests up to 1,000 models per page while preserving existing query parameters
• resets stale initial page tokens and forwards opaque tokens safely
• de-duplicates model IDs in deterministic first-seen order
• fails closed on malformed or failed later pages, token cycles, and more than 20 pages
• keeps the existing parseGoogleModels string-array API and adds no dependencies

Why

The keyed Google refresh previously fetched only one response. Google defaults models.list to 50 records per page, so valid current models after page one could be silently omitted.

Validation

• node refresh/test/run.mjs
• npm test
• node --check refresh/providers.mjs
• node --check refresh/test/run.mjs
• git diff --check

Closes #76