Update agent model presets to latest Anthropic/Google models and add Antigravity CLI support

[Saber-Yemen]

Request

Please refresh the built-in agent/provider model presets to current Anthropic and Google model generations, and add a migration path for Google's CLI transition.

Why

I could not find an existing issue that covers this end to end.

The closest items I found were:

• fix(agents): refresh provider model presets #556 / fix(agents): refresh provider model presets #555 - refresh provider model presets
• Gemini 3.0 Pro support missing #423 - Gemini 3.0 Pro support missing
• I think I'm holding it wrong? Your fork/implementation of Codex explains that we can use Anthropic models. #499 - Anthropic model selection confusion

As of May 25, 2026, the Google and Anthropic agent defaults still look behind the current model and CLI landscape.

Requested updates

• Add/update Anthropic presets for Claude Opus 4.7
• Refresh Google presets to the latest Gemini family you want to target, specifically Gemini 3.5 Flash and Gemini 3.1 Pro if those are the intended current defaults
• Add support for Antigravity CLI as the forward path for Google agent integration
• Keep compatibility aliases and config migration paths for older slugs so existing configs do not break

Important context

Google announced on May 19, 2026 that Gemini CLI is transitioning to Antigravity CLI:

• https://developers.googleblog.com/en/an-important-update-transitioning-gemini-cli-to-antigravity-cli/
• https://antigravity.google/docs/gcli-migration

That announcement says Gemini CLI stops serving requests for consumer/free usage on June 18, 2026, while some enterprise and API-key based access remains supported. Even with that nuance, Antigravity CLI appears to be the forward path and is worth supporting alongside or ahead of Gemini CLI.

Suggested implementation scope

• Refresh built-in model presets to current provider model IDs
• Add Antigravity CLI detection/invocation, or at least a dual-path migration period with Gemini CLI
• Update docs, prompts, examples, and tests to match the new defaults
• Preserve backward compatibility via alias upgrades and config rewrites where possible

Thanks - this would make the agent defaults feel current again and reduce Google-side breakage as the CLI transition rolls forward.