Add Gemini 4 Argon and reasoning effort to Gemini Computer Use

[NikhilShahi]

Summary

Expose the API's new gemini-4-argon model and optional reasoningEffort for Gemini Computer Use (hyperbrowserai/browserctrl#1580). Gemini 3.8 Flash remains the default, and omitting reasoningEffort keeps each model's existing behavior.

Changes

• Add "gemini-4-argon" to GeminiComputerUseLlm.
• Add and export GeminiComputerUseReasoningEffort ("minimal" | "low" | "medium" | "high"), and add reasoningEffort to StartGeminiComputerUseTaskParams. The API rejects "minimal" for Argon, 3.8 Flash, and 3.7 Flash.
• Add an HTTP integration test for the start payload (Argon with effort and BYOK keys, 3.6 Flash with minimal, and Argon with effort omitted).
• Bump the version to 1.2.2.

await client.agents.geminiComputerUse.startAndWait({
  task: "Go to Hacker News and tell me the title of the top post",
  llm: "gemini-4-argon",
  reasoningEffort: "high",
});

Validation

• yarn lint
• yarn build (via yarn install)
• yarn typecheck
• yarn test: 737 passed
• A live call against production returned 400 because it still lists only the older Gemini models, so #1580 isn't deployed yet. Re-run a live Argon task once it ships.