fix: remove deprecated Gemini image models

[clawdvader]

Summary

• Removes retired Gemini image model IDs from the TypeScript SDK supported Gemini model list
• Updates the Next image template to use the stable gemini-2.5-flash-image model
• Removes the deleted model from the provider smoke-test blacklist

Verification

• corepack pnpm install --frozen-lockfile completed and ran the SDK prepare build successfully
• corepack pnpm -C packages/sdk/ts run build passed
• git diff --check passed
• Attempted npm run build in templates/next-image; it is blocked by existing template dependency resolution issues unrelated to this change (lucide-react peer range with React 19, then missing zod/v3/v4 from latest SDK install)

/claim #634

[vercel]

@clawdvader is attempting to deploy a commit to the Merit Systems Team on Vercel.

A member of the Team first needs to authorize it.