[Claimed #2940] feat(integrations): update default Google model to gemini-3.8-flash

[github-actions]

Mirrored from external contributor PR #2940 after approval by @miguelg719.

Original author: @antonvishal
Original PR: #2940
Approved source head SHA: 6503a8b9ea82b39a0a4f34d7ceaa7110c677661b

@antonvishal, please continue any follow-up discussion on this mirrored PR. When the external PR gets new commits, this same internal PR will be marked stale until the latest external commit is approved and refreshed here.

Original description

Summary

Updates the inferred default Google Gemini model in integrations from google/gemini-3.6-flash to google/gemini-3.8-flash, and updates the Eve integration README.

Part of breaking up #2920 into 3 PRs as requested in #2920 (comment) (integrations).

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Summary by cubic

Updates the default Google model for inferred Stagehand integrations from google/gemini-3.6-flash to google/gemini-3.8-flash.

• Updates the Eve integration README to document the new default.

^{Written for commit 6503a8b. Summary will update on new commits.}

[github-actions]

This mirrored PR has been merged into main. The original external PR #2940 is now completed.

[changeset-bot]

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Latest commit: 6503a8b

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