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/BreadcrumbBar.tsx

@@ -0,0 +1,43 @@
+import { Link } from "react-router-dom";
+import { useBreadcrumbs } from "../context/BreadcrumbContext";
+import {
+  Breadcrumb,
+  BreadcrumbItem,
+  BreadcrumbLink,
+  BreadcrumbList,
+  BreadcrumbPage,
+  BreadcrumbSeparator,
+} from "@/components/ui/breadcrumb";
+import { Fragment } from "react";
+
+export function BreadcrumbBar() {
+  const { breadcrumbs } = useBreadcrumbs();
+
+  if (breadcrumbs.length === 0) return null;
+
+  return (
+    <div className="border-b border-border px-6 py-2">
+      <Breadcrumb>
+        <BreadcrumbList>
+          {breadcrumbs.map((crumb, i) => {
+            const isLast = i === breadcrumbs.length - 1;
+            return (
+              <Fragment key={i}>
+                {i > 0 && <BreadcrumbSeparator />}
+                <BreadcrumbItem>
+                  {isLast || !crumb.href ? (
+                    <BreadcrumbPage>{crumb.label}</BreadcrumbPage>
+                  ) : (
+                    <BreadcrumbLink asChild>
+                      <Link to={crumb.href}>{crumb.label}</Link>
+                    </BreadcrumbLink>
+                  )}
+                </BreadcrumbItem>
+              </Fragment>
+            );
+          })}
+        </BreadcrumbList>
+      </Breadcrumb>
+    </div>
+  );
+}