Admin UX overhaul: P0 fixes, error-UX foundations, nav cleanup, tenant detail page

From the 2026-07-14 UI/UX audit (17/40). Four phases:

P1 — Settings route crashed on Agents→Edit (Input/Textarea used but never
imported). Added imports + a shared route-level error boundary
(components/route-error.tsx) re-exported from all shell routes, so one
crashing panel degrades to an explained card with the nav intact instead of
replacing the whole app with a stack trace. Corrected the stale CLAUDE.md
claim that `npm run typecheck` crashes — it works, and would have caught the
missing import.

P2 — Error/empty/feedback foundations. Fixed useSession identity churn that
fired ~3x duplicate fetches per screen and self-inflicted 429s (referentially
stable snapshot). New lib/errors.ts (describeError → plain-language + the fix)
and components/data-state.tsx (DataState renders exactly one of
error/loading/empty/content, so a failed load never shows as "empty";
DialogError for in-dialog failures; 429 auto-retry). Rolled across all 15
list routes; every mutation now toasts. Surfaced+fixed two silent-failure
bugs (sso + buckets-CORS swallowed load errors; the latter could wipe rules
on save).

P3 — Nav IA + trust cleanup. Default-expanded rail; regrouped into 7 coherent
sections; collapsed the Apps/Plan/Entitlements stub triplication into one
honest /billing page; deleted fabricated seeded notifications and the dead
Help menu item; fixed the 403 copy (referenced a tenant switcher that doesn't
exist); removed orphan /assistant + /library routes; gated dev-seed login
hints behind DEV; renamed /activity → /audit-log with a redirect.

P4 — Tenant detail page (routes/tenants.$id.tsx + components/tenant-detail/*),
closing the provision→configure gap. 8 tabs (Overview, Plan & quotas,
Branding, Localization, Email & SMS, Feature flags, IP rules, Inbound
webhooks), each verified saving to the real backend. Row name links to detail.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

app/lib/notifications.ts

@@ -2,7 +2,7 @@
 // Pair with @crema/notification-ui's <ToastProvider /> for transient toasts;
 // this store is for the appbar bell's persistent inbox.
 
-import { useEffect, useSyncExternalStore } from "react"
+import { useSyncExternalStore } from "react"
 
 export type NotificationKind = "info" | "success" | "warning" | "error"
 
@@ -95,11 +95,27 @@ export function dismissAll() {
   writeToStorage([])
 }
 
-let cached: AppNotification[] | null = null
+// Cache keyed on the raw stored string so the snapshot stays referentially
+// stable — `useSyncExternalStore` requires that getSnapshot return the same
+// reference until the value genuinely changes. (This used to clear a flag on
+// every mount without notifying subscribers, the same identity-churn bug that
+// was fixed in session.ts.)
+let cached: AppNotification[] = []
+let cachedRaw: string | null = null
+let primed = false
+
+function readRaw(): string | null {
+  if (typeof window === "undefined") return null
+  try {
+    return localStorage.getItem(STORAGE_KEY)
+  } catch {
+    return null
+  }
+}
 
 function subscribe(cb: () => void): () => void {
   const onChange = () => {
-    cached = null
+    primed = false
     cb()
   }
   window.addEventListener(CHANGE_EVENT, onChange)
@@ -109,7 +125,12 @@ function subscribe(cb: () => void): () => void {
   return () => window.removeEventListener(CHANGE_EVENT, onChange)
 }
 function getSnapshot(): AppNotification[] {
-  if (!cached) cached = readFromStorage()
+  const raw = readRaw()
+  if (!primed || raw !== cachedRaw) {
+    cachedRaw = raw
+    cached = readFromStorage()
+    primed = true
+  }
   return cached
 }
 function getServerSnapshot(): AppNotification[] {
@@ -117,39 +138,9 @@ function getServerSnapshot(): AppNotification[] {
 }
 
 export function useNotifications(): AppNotification[] {
-  const value = useSyncExternalStore(subscribe, getSnapshot, getServerSnapshot)
-  useEffect(() => {
-    cached = null
-  }, [])
-  return value
+  return useSyncExternalStore(subscribe, getSnapshot, getServerSnapshot)
 }
 
 export function unreadCount(items: AppNotification[]): number {
   return items.filter((n) => !n.readAt).length
 }
-
-/** Seed a few demo notifications on first load so the bell isn't empty. */
-export function seedIfEmpty() {
-  if (typeof window === "undefined") return
-  if (localStorage.getItem(STORAGE_KEY)) return
-  const now = Date.now()
-  const seed: AppNotification[] = [
-    {
-      id: newId(),
-      kind: "info",
-      title: "Welcome",
-      body: "Tag elements with data-action and the assistant can drive them.",
-      href: "/assistant",
-      createdAt: now - 60_000,
-    },
-    {
-      id: newId(),
-      kind: "success",
-      title: "Profile saved",
-      body: "Your display name and avatar are live across the app.",
-      href: "/profile",
-      createdAt: now - 5 * 60_000,
-    },
-  ]
-  writeToStorage(seed)
-}