docs: remove references to deprecated preview features toggle

[AadithyaAle]

Summary

This PR removes outdated references to the "Preview Features" toggle in the documentation.

Details

As of v0.29.0, Gemini 3 models are enabled by default and the previewFeatures toggle has been removed from the codebase. This PR cleans up docs/get-started/gemini-3.md and docs/cli/model.md to prevent user confusion.

Related Issues

Fixes #20415

How to Validate

Verified that the documentation no longer refers to non-existent settings and matches the current v0.30.0 CLI behavior.

Pre-Merge Checklist

• Updated relevant documentation and README (if needed)
• Added/updated tests (if needed)
• Noted breaking changes (if any)
• Validated on required platforms/methods:
  • MacOS
    • npm run
    • npx
    • Docker
    • Podman
    • Seatbelt
  • Windows
    • npm run
    • npx
    • Docker
  • Linux
    • npm run
    • npx
    • Docker

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[gemini-code-assist]

Summary of Changes

Hello @AadithyaAle, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request updates the documentation to reflect that Gemini 3 is now the default model family in the Gemini CLI, eliminating the need for a manual 'Preview Features' toggle. This change streamlines the user experience by removing deprecated instructions and clarifying the new default behavior for model access.

Highlights

• Gemini 3 Default: Updated documentation to reflect Gemini 3 as the default model family in the Gemini CLI, starting from v0.29.0.
• Deprecated Feature Toggle Removal: Removed all references and instructions related to the deprecated 'Preview Features' toggle for Gemini 3 enablement.
• Streamlined Access Instructions: Streamlined instructions for accessing Gemini 3, emphasizing automatic availability with the latest CLI version and removing manual enablement steps.

Changelog

• docs/cli/model.md
  • Modified the model table to remove '(if enabled)' from Gemini 3 model descriptions, indicating their default availability.
  • Renamed the section 'Gemini 3 and preview features' to 'Gemini 3 Default' to reflect the updated status.
  • Added a note explaining that Gemini 3 is now the default as of v0.29.0 and no longer requires a manual feature flag.
  • Removed the instruction to enable 'Preview Features' via the settings command.
• docs/get-started/gemini-3.md
  • Removed a sentence indicating that Gemini 3 Pro requires two steps (administrative and user enablement) for configuration.
  • Revised the steps for accessing Gemini 3, replacing the 'Preview Features' toggle instructions with guidance to restart the CLI and ensure the latest version, noting automatic access.

Activity

• No human activity has occurred on this pull request yet.

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[gemini-code-assist]

Code Review

This pull request updates the documentation to remove references to the deprecated 'preview features' toggle, reflecting that Gemini 3 models are now enabled by default. The changes in docs/get-started/gemini-3.md are correct and clearly update the user instructions. However, in docs/cli/model.md, the update has left behind some duplicated text and a dangling link. I've added a comment with a suggestion to clean this up.

[AadithyaAle]

"Thanks for the catch! I've updated the file to remove the duplicated text and the dangling link. The documentation now accurately reflects the v0.29.0 default behavior."