fix(core): nav sidebar should have default bg (#13265)

fix AF-2724

#### PR Dependency Tree


* **PR #13265** 👈

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[Charcoal](https://github.com/danerwilliams/charcoal)

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## Summary by CodeRabbit

* **Style**
* Updated sidebar background color to apply in additional display
scenarios, ensuring a more consistent appearance across different modes.

<!-- end of auto-generated comment: release notes by coderabbit.ai -->

packages/frontend/core/src/modules/app-sidebar/views/index.css.ts

@@ -13,7 +13,7 @@ export const navWrapperStyle = style({
     '&[data-has-border=true]': {
       borderRight: `0.5px solid ${cssVarV2('layer/insideBorder/border')}`,
     },
-    '&[data-is-floating="true"]': {
+    '&[data-is-floating="true"], &[data-is-electron="false"]': {
       backgroundColor: cssVarV2('layer/background/primary'),
     },
   },