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/hooks/useKeyboardShortcuts.ts

@@ -0,0 +1,40 @@
+import { useEffect } from "react";
+
+interface ShortcutHandlers {
+  onNewIssue?: () => void;
+  onToggleSidebar?: () => void;
+  onTogglePanel?: () => void;
+}
+
+export function useKeyboardShortcuts({ onNewIssue, onToggleSidebar, onTogglePanel }: ShortcutHandlers) {
+  useEffect(() => {
+    function handleKeyDown(e: KeyboardEvent) {
+      // Don't fire shortcuts when typing in inputs
+      const target = e.target as HTMLElement;
+      if (target.tagName === "INPUT" || target.tagName === "TEXTAREA" || target.isContentEditable) {
+        return;
+      }
+
+      // C → New Issue
+      if (e.key === "c" && !e.metaKey && !e.ctrlKey && !e.altKey) {
+        e.preventDefault();
+        onNewIssue?.();
+      }
+
+      // [ → Toggle Sidebar
+      if (e.key === "[" && !e.metaKey && !e.ctrlKey) {
+        e.preventDefault();
+        onToggleSidebar?.();
+      }
+
+      // ] → Toggle Panel
+      if (e.key === "]" && !e.metaKey && !e.ctrlKey) {
+        e.preventDefault();
+        onTogglePanel?.();
+      }
+    }
+
+    document.addEventListener("keydown", handleKeyDown);
+    return () => document.removeEventListener("keydown", handleKeyDown);
+  }, [onNewIssue, onToggleSidebar, onTogglePanel]);
+}