[breaking] Google schedules embedding-2-preview shutdown for August 10, 2026

The Gemini deprecations schedule lists embedding-2-preview (released March 10, 2026) for earliest shutdown August 10, 2026, replaced by gemini-embedding-2. The changelog carries no dated announcement; announced_at reflects the capture date. Effective: 2026-08-10. Migration target: google/gemini-embedding-2. Affected: google/embedding-2-preview. Severity: breaking. Verification: verified.