feat: move projects to sidebar rail and speed up session switching (#506)

* feat: move projects from header tabs to left sidebar rail

* refactor: remove variant from git generation session context

* feat: implemented drandrop action for navrails

* refactor: improve sidebar drag-and-drop smoothness and remove floating overlay

* fix: prevent mobile nav rail touch from closing drawer and opening menu

* fix: hide header tabs on desktop

* fix: prevent session flicker when switching projects

* style: soften chat panel divider borders

* style: improve icon contrast across core navigation

* fix: stabilize session selection during project switching

* style: unify sidebar surfaces and transparent section layers

* style: remove UI shadows and keep only scroll shadow

* perf: speed up project switching with cached session loading

* perf: speed up Git changes view and background refresh

* perf: make session switching lighter and less aggressive

* perf: optimized sessions list loading while project switching

* perf: smooth chat rendering and reduce interaction spikes

* fix: restore reliable load older messages visibility

packages/ui/src/components/multirun/ModelMultiSelect.tsx

@@ -379,7 +379,7 @@ export const ModelMultiSelect: React.FC<ModelMultiSelectProps> = ({
             let currentFlatIndex = 0;
 
             return (
-              <div style={{ backgroundColor: 'var(--surface-elevated)' }} className="absolute bottom-full left-0 mb-1 z-50 border border-border/30 rounded-xl overflow-hidden shadow-lg w-[min(380px,calc(100vw-2rem))] flex flex-col">
+              <div style={{ backgroundColor: 'var(--surface-elevated)' }} className="absolute bottom-full left-0 mb-1 z-50 border border-border/30 rounded-xl overflow-hidden shadow-none w-[min(380px,calc(100vw-2rem))] flex flex-col">
                 {/* Search input */}
                 <div className="p-2 border-b border-border/40">
                   <div className="relative">