Knowledge base + grouped, reordered sidebar

Adds an in-app Knowledge base (route /help): 15 searchable, expandable how-to articles
with step-by-step guides and examples (concepts, A-to-Z setup, the review inbox, the
handoff + memory, the libraries, analytics, governance, troubleshooting), rendered as
markdown.

Reorganizes the sidebar into UX-ordered groups with section labels — Get started ·
Work (Board/Team/Cartable/Reviews) · Organization (Structure/Org chart/Members) ·
AI & libraries (AI seats/Skills/Agent profiles/Product profiles) · Insights
(Performance/Analytics) · Help (Knowledge base).

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

client/src/components/AppShell.tsx

@@ -2,6 +2,7 @@ import type { ReactNode } from 'react'
 import { Link, useLocation } from 'react-router'
 import {
   BookMarked,
+  BookOpen,
   BookUser,
   Bot,
   Boxes,
@@ -45,21 +46,32 @@ export function AppShell({ children }: { children: ReactNode }) {
 
         <Separator className="bg-sidebar-border" />
 
-        <nav className="flex flex-1 flex-col gap-1 p-3">
+        <nav className="flex flex-1 flex-col gap-0.5 overflow-y-auto p-3">
           <NavItem icon={Rocket} label="Get started" to="/start" />
+
+          <NavSection label="Work" />
           <NavItem icon={LayoutDashboard} label="Board" to="/" />
           <NavItem icon={Sparkles} label="Team" to="/team" />
           <NavItem icon={Inbox} label="Cartable" to="/cartable" />
           <NavItem icon={ShieldCheck} label="Review inbox" to="/reviews" />
-          <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" />
+
+          <NavSection label="Organization" />
           <NavItem icon={Boxes} label="Structure" to="/structure" />
+          <NavItem icon={Network} label="Org chart" to="/org" />
           <NavItem icon={Users} label="Members" to="/members" />
+
+          <NavSection label="AI & libraries" />
+          <NavItem icon={Bot} label="AI seats" to="/seats" />
+          <NavItem icon={BookMarked} label="Skills" to="/skills" />
+          <NavItem icon={BookUser} label="Agent profiles" to="/agent-profiles" />
+          <NavItem icon={Package} label="Product profiles" to="/product-profiles" />
+
+          <NavSection label="Insights" />
           <NavItem icon={Gauge} label="Performance" to="/performance" />
           <NavItem icon={ChartColumn} label="Analytics" to="/analytics" />
+
+          <NavSection label="Help" />
+          <NavItem icon={BookOpen} label="Knowledge base" to="/help" />
         </nav>
 
         <Separator className="bg-sidebar-border" />
@@ -83,6 +95,14 @@ export function AppShell({ children }: { children: ReactNode }) {
   )
 }
 
+function NavSection({ label }: { label: string }) {
+  return (
+    <div className="px-3 pb-1 pt-4 text-[10px] font-semibold uppercase tracking-wider text-sidebar-foreground/45">
+      {label}
+    </div>
+  )
+}
+
 function NavItem({
   icon: Icon,
   label,