bug: gdal required

**Describe the bug**
When installing and running sb as instructed in the docs, I get the error message that gdal is required.

**To Reproduce**
Install and run as shown in docs.

**Expected behavior**
Runs.

**Screenshots**

**Desktop (please complete the following information):**
- OS: Mac OS 15.7.7

**You have a solution? (optional)**
Yes, I just needed to install/add gdal to the environment (it exists on conda).

**Additional context**
Probably a note in the install docs would be enough to fix this.

Start with the installation documentation and follow the documented setup on macOS. Update the relevant install instructions to note that GDAL must be installed or added to the environment, then verify that the documented setup runs without the reported requirement error.

Written by the indexing model from the issue text.