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/context/DialogContext.tsx

@@ -0,0 +1,45 @@
+import { createContext, useCallback, useContext, useState, type ReactNode } from "react";
+
+interface NewIssueDefaults {
+  status?: string;
+  priority?: string;
+  projectId?: string;
+}
+
+interface DialogContextValue {
+  newIssueOpen: boolean;
+  newIssueDefaults: NewIssueDefaults;
+  openNewIssue: (defaults?: NewIssueDefaults) => void;
+  closeNewIssue: () => void;
+}
+
+const DialogContext = createContext<DialogContextValue | null>(null);
+
+export function DialogProvider({ children }: { children: ReactNode }) {
+  const [newIssueOpen, setNewIssueOpen] = useState(false);
+  const [newIssueDefaults, setNewIssueDefaults] = useState<NewIssueDefaults>({});
+
+  const openNewIssue = useCallback((defaults: NewIssueDefaults = {}) => {
+    setNewIssueDefaults(defaults);
+    setNewIssueOpen(true);
+  }, []);
+
+  const closeNewIssue = useCallback(() => {
+    setNewIssueOpen(false);
+    setNewIssueDefaults({});
+  }, []);
+
+  return (
+    <DialogContext.Provider value={{ newIssueOpen, newIssueDefaults, openNewIssue, closeNewIssue }}>
+      {children}
+    </DialogContext.Provider>
+  );
+}
+
+export function useDialog() {
+  const ctx = useContext(DialogContext);
+  if (!ctx) {
+    throw new Error("useDialog must be used within DialogProvider");
+  }
+  return ctx;
+}