Feature Request: Isolate "Initial Layer Line Width" from specific wall/infill line width settings

Is your feature request related to a problem?

Yes. Currently, the Initial Layer Line Width acts as a percentage multiplier based on standard line width settings (Outer Wall, Inner Wall, Infill, Top/Bottom). If I tune the outer wall line width to achieve better details or surface quality on the rest of the print, it unintentionally modifies the first layer's wall line width.

The first layer is critical for bed adhesion. To achieve perfect adhesion and first-layer consistency, users need absolute and isolated control over this layer. Having it depend on other geometric parameters makes fine-tuning first-layer adhesion unpredictable and frustrating.

Describe the solution you'd like

I would like the Initial Layer Line Width to be completely decoupled from the subsequent specific line width parameters (like outer/inner walls or infill). The first layer line width should only be bound to:

1. The physical Nozzle Size.
2. The specific Initial Layer Line Width parameter (either as a pure percentage of the global/nozzle width).

This would allow users to alter wall thicknesses for the upper layers without destroying a well-calibrated first-layer setup.

Describe alternatives you've considered

Manually recalculating and changing the Initial Layer Line Width percentage every single time any other line width setting is altered, which is prone to human error.

Affected users and/or printers

This affects all FDM printing workflows where bed adhesion is critical or when printing technical materials that require precise first-layer squish.

Additional information & file uploads

No response