add gemini-3.5-flash to gemini computer use

[NikhilShahi]

Summary

Changes

Validation

• yarn lint
• yarn build

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Note

Low Risk
SDK-only type and version bump with no runtime logic changes; risk is limited to consumers relying on the expanded LLM union matching the API.

Overview
Adds gemini-3.5-flash as a selectable model on the GeminiComputerUseLlm union in src/types/constants.ts, so Gemini computer-use tasks can type-check when passing that llm value (e.g. on StartGeminiComputerUseTaskParams).

Bumps the package version from 0.91.0 to 0.91.1 for release.

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