Product profiles page — frontend (Slice 4)

A new "Product profiles" page (library + marketplace) mirroring the agent-profile
library: upload/author a PRODUCT.md (Markdown editor), view, edit, new version, fork
builtins, publish/unpublish, install from marketplace, and Apply-to-product (sets the
chosen product's shared identity). Reuses groupVersions + MarkdownEditor; adds the
route and a sidebar entry.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

client/src/components/AppShell.tsx

@@ -12,6 +12,7 @@ import {
   LayoutDashboard,
   LogOut,
   Network,
+  Package,
   ShieldCheck,
   Users,
 } from 'lucide-react'
@@ -46,6 +47,7 @@ export function AppShell({ children }: { children: ReactNode }) {
           <NavItem icon={Bot} label="AI seats" to="/seats" />
           <NavItem icon={BookUser} label="Agent profiles" to="/agent-profiles" />
           <NavItem icon={BookMarked} label="Skills" to="/skills" />
+          <NavItem icon={Package} label="Product profiles" to="/product-profiles" />
           <NavItem icon={Network} label="Org chart" to="/org" />
           <NavItem icon={Boxes} label="Structure" to="/structure" />
           <NavItem icon={Users} label="Members" to="/members" />