docs: Add instructions for MacPorts and uninstall instructions for Homebrew (#17412)

Signed-off-by: Nils Breunese <nils@breun.nl>
Co-authored-by: Jack Wotherspoon <jackwoth@google.com>

Author: breun

README.md

@@ -55,6 +55,12 @@ npm install -g @google/gemini-cli
 brew install gemini-cli
 ```
 
+#### Install globally with MacPorts (macOS)
+
+```bash
+sudo port install gemini-cli
+```
+
 #### Install with Anaconda (for restricted environments)
 
 ```bash

docs/cli/uninstall.md

@@ -45,3 +45,21 @@ npm uninstall -g @google/gemini-cli
 ```
 
 This command completely removes the package from your system.
+
+## Method 3: Homebrew
+
+If you installed the CLI globally using Homebrew (e.g.,
+`brew install gemini-cli`), use the `brew uninstall` command to remove it.
+
+```bash
+brew uninstall gemini-cli
+```
+
+## Method 4: MacPorts
+
+If you installed the CLI globally using MacPorts (e.g.,
+`sudo port install gemini-cli`), use the `port uninstall` command to remove it.
+
+```bash
+sudo port uninstall gemini-cli
+```