fix(session-list): remove group-hover fade on project header action icons

The folder/terminal/browser icons in the project header used opacity-50 +
group-hover:opacity-100, causing all three to fade in together when
hovering anywhere on the project row. Switch to per-icon hover only so
each icon behaves like every other icon button in the app.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: liyakhar

packages/desktop/src/lib/acp/components/session-list/session-list-ui.svelte

@@ -607,7 +607,7 @@ function handleOpenGitPanel(event: MouseEvent, projectPath: string) {
 }
 
 const projectHeaderHoverActionButtonClass =
-	"flex items-center justify-center size-5 rounded text-muted-foreground transition-all hover:bg-accent hover:text-foreground opacity-50 group-hover:opacity-100 group-focus-within:opacity-100 focus-visible:opacity-100";
+	"flex items-center justify-center size-5 rounded text-muted-foreground transition-colors hover:bg-accent hover:text-foreground";
 
 function handleOpenFileExplorer(event: MouseEvent, group: SessionGroup): void {
 	event.stopPropagation();