Bug report: Saturation param from theme URL config is never parsed

[teyepe]

Description

When opening a Leonardo theme URL that has a saturation parameter other than 100%, the web UI doesn't read the actual saturation value and always defaults to 100%.

Steps to reproduce

1. Open this url in web UI.
2. Decode the above URL to see that "saturation": 20.
3. In web UI, open Theme Settings. Saturation slider shows 100% instead of 20%.

Expected behavior

When a theme URL contains a saturation parameter in the config object, the web UI should:

1. Parse the saturation value from the URL
2. Adjust the saturation slider to the specified value
3. Apply the saturation to the theme's _theme.saturation property
4. Update the saturation display label to show the correct percentage

Root Cause

In docs/ui/src/js/params.js, the paramSetup() function handles URL parameter parsing but does not include any logic to parse or apply the saturation parameter.

Code Location

File: docs/ui/src/js/params.js
Function: paramSetup()
Lines: After line 116 (between contrast handling and Promise.all)