Add shared UI primitives, contexts, and reusable components

Add shadcn components: avatar, breadcrumb, checkbox, collapsible,
command, dialog, dropdown-menu, label, popover, scroll-area, sheet,
skeleton, tabs, textarea, tooltip. Add shared components: BreadcrumbBar,
CommandPalette, CompanySwitcher, CommentThread, EmptyState, EntityRow,
FilterBar, InlineEditor, MetricCard, PageSkeleton, PriorityIcon,
PropertiesPanel, StatusIcon, SidebarNavItem/Section. Add contexts for
breadcrumbs, dialogs, and side panels. Add keyboard shortcut hook and
utility helpers. Update layout, sidebar, and main app shell.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

ui/src/components/EntityRow.tsx

@@ -0,0 +1,52 @@
+import { type ReactNode } from "react";
+import { cn } from "../lib/utils";
+
+interface EntityRowProps {
+  leading?: ReactNode;
+  identifier?: string;
+  title: string;
+  subtitle?: string;
+  trailing?: ReactNode;
+  selected?: boolean;
+  onClick?: () => void;
+  className?: string;
+}
+
+export function EntityRow({
+  leading,
+  identifier,
+  title,
+  subtitle,
+  trailing,
+  selected,
+  onClick,
+  className,
+}: EntityRowProps) {
+  return (
+    <div
+      className={cn(
+        "flex items-center gap-3 px-4 py-2 text-sm border-b border-border last:border-b-0 transition-colors",
+        onClick && "cursor-pointer hover:bg-accent/50",
+        selected && "bg-accent/30",
+        className
+      )}
+      onClick={onClick}
+    >
+      {leading && <div className="flex items-center gap-2 shrink-0">{leading}</div>}
+      <div className="flex-1 min-w-0">
+        <div className="flex items-center gap-2">
+          {identifier && (
+            <span className="text-xs text-muted-foreground font-mono shrink-0">
+              {identifier}
+            </span>
+          )}
+          <span className="truncate">{title}</span>
+        </div>
+        {subtitle && (
+          <p className="text-xs text-muted-foreground truncate mt-0.5">{subtitle}</p>
+        )}
+      </div>
+      {trailing && <div className="flex items-center gap-2 shrink-0">{trailing}</div>}
+    </div>
+  );
+}