docs(21-01): create summary and update state for error boundary + toasts

.planning/STATE.md

@@ -233,6 +233,10 @@ Recent decisions affecting current work:
 - 20-02: Subscription-driven invalidation (not local state) — simplest approach, reuses existing React Query cache
 - 20-02: Silent onError callbacks — pages degrade to manual refresh when backend is not running
 - 20-02: No new packages needed — splitLink and httpSubscriptionLink ship with @trpc/client v11
+- 21-01: ErrorBoundary wraps Outlet only (not entire AppLayout) so nav shell survives render errors
+- 21-01: Toaster outside AppLayout as sibling — available even if layout breaks
+- 21-01: notFoundComponent uses shadcn Button with asChild + Link (consistent with component library)
+- 21-01: One success and one error toast per mutation — no toasts for query failures (those have inline error states)
 - 21-02: Skeleton component in components/ (not ui/) — app-specific, not a shadcn primitive
 - 21-02: Inbox skeleton lives in inbox.tsx route (not InboxList component) since InboxList receives pre-loaded data
 - 21-03: Removed disabled nav stubs (Agents, Tasks, Settings) — stubs create false promises for v2.0