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/views/git/PullRequestSection.tsx

@@ -698,7 +698,7 @@ export const PullRequestSection: React.FC<{
           </div>
         ) : null}
         {run.output?.text ? (
-          <div className="rounded border border-border/40 bg-background/40 px-2 py-2 typography-micro text-muted-foreground whitespace-pre-wrap max-h-48 overflow-y-auto">
+          <div className="rounded border border-border/40 bg-transparent px-2 py-2 typography-micro text-muted-foreground whitespace-pre-wrap max-h-48 overflow-y-auto">
             {run.output.text}
           </div>
         ) : null}
@@ -776,7 +776,7 @@ export const PullRequestSection: React.FC<{
                       {step.conclusion ? <span className="ml-auto flex-shrink-0">{step.conclusion}</span> : null}
                     </button>
                     <CollapsibleContent>
-                      <div className="ml-6 mt-1 rounded border border-border/40 bg-background/40 px-2 py-2 typography-micro text-muted-foreground space-y-1">
+                      <div className="ml-6 mt-1 rounded border border-border/40 bg-transparent px-2 py-2 typography-micro text-muted-foreground space-y-1">
                         {typeof step.number === 'number' ? <div>Step: {step.number}</div> : null}
                         {step.status ? <div>Status: {step.status}</div> : null}
                         {step.conclusion ? <div>Conclusion: {step.conclusion}</div> : null}
@@ -1304,7 +1304,7 @@ export const PullRequestSection: React.FC<{
 
   const containerClassName =
     variant === 'framed'
-      ? 'rounded-xl border border-border/60 bg-background/70 overflow-hidden'
+      ? 'rounded-xl border border-border/60 bg-transparent overflow-hidden'
       : 'border-0 bg-transparent rounded-none';
   const headerClassName =
     variant === 'framed'