Remove Homebrew from recommended installation methods or provide an official tap

### URL of the page with the issue

https://geminicli.com/docs/get-started/installation/#install-gemini-cli

### What is the problem?

According to `docs/get-started/installation.mdx` and `README.md`, Homebrew is listed as one of the recommended installation methods for Gemini CLI.

However, `gemini-cli` is currently marked as deprecated in `homebrew-core`, and it does not seem likely that this will be reverted.

Reference: Homebrew/homebrew-core#289444

> We don't have a way to make a distinction between the general public and enterprise customers, so we deprecate based on the situation the default user will find themselves in.

Given this situation, the current documentation may be misleading for general users.

### What did you expect to happen?

Would you consider one of the following?

- Removing Homebrew from the recommended installation methods
- Providing an official tap for Homebrew users

### Additional context

_No response_

Start with docs/get-started/installation.mdx and README.md, then review the linked Homebrew deprecation context. Confirm how Homebrew is currently presented and update the affected documentation once the project chooses between removing it and documenting an official tap; done means the installation guidance no longer misleads users.

Written by the indexing model from the issue text.