fix+upstream: hooks-order crash, ConfirmDialog/PageHeader/skeletons, styled error boundary

Hoists hooks above early return (render-time Navigate); ports finance's
ConfirmDialog/PageHeader/loading/states + APC error-copy mapper; removes
window.confirm, dead appbar search, and seeded fake notifications; wires toasts.

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

app/lib/errors.ts

@@ -0,0 +1,73 @@
+// Human error copy. Maps error codes / shapes / thrown values to a single
+// plain sentence a person can act on. Used by the root ErrorBoundary and
+// available to any route that catches a failure (e.g. a fetch reject).
+//
+// Ported/generalised from arcadia-personal-cloud-web's `acceptErrorMessage`:
+// switch on a known machine `code`, else flatten field-validation errors,
+// else fall back to the raw message or a friendly default.
+
+import { isRouteErrorResponse } from "react-router"
+
+/** A known machine error code → the human sentence we show for it. Extend
+ *  this map as the app grows real backend error codes. */
+const CODE_MESSAGES: Record<string, string> = {
+  network_error: "Couldn't reach the server. Check your connection and try again.",
+  timeout: "That took too long to respond. Try again in a moment.",
+  unauthorized: "Your session has expired. Sign in again to continue.",
+  forbidden: "You don't have access to that.",
+  not_found: "We couldn't find what you were looking for.",
+  rate_limited: "Too many requests just now. Give it a few seconds.",
+  server_error: "Something went wrong on our end. Try again shortly.",
+}
+
+type ErrorShape = {
+  error?: string
+  code?: string
+  message?: string
+  errors?: Record<string, string[] | string>
+}
+
+/** Turn any caught value into one human sentence. */
+export function humanErrorMessage(err: unknown): string {
+  // React Router route-error responses (thrown Responses / 404s etc.).
+  if (isRouteErrorResponse(err)) {
+    if (err.status === 404) return CODE_MESSAGES.not_found
+    if (err.status === 401) return CODE_MESSAGES.unauthorized
+    if (err.status === 403) return CODE_MESSAGES.forbidden
+    if (err.status === 429) return CODE_MESSAGES.rate_limited
+    if (err.status >= 500) return CODE_MESSAGES.server_error
+    return err.statusText || "That request couldn't be completed."
+  }
+
+  const d = (
+    err && typeof err === "object" ? err : {}
+  ) as ErrorShape
+  const code = d.code ?? d.error
+  if (code && CODE_MESSAGES[code]) return CODE_MESSAGES[code]
+
+  // arcadia-style field validation: { errors: { field: [msg...] } } —
+  // flatten into a single readable line so the user knows what to fix.
+  if (d.errors && typeof d.errors === "object") {
+    const lines: string[] = []
+    for (const [field, msgs] of Object.entries(d.errors)) {
+      const label = field.replace(/_/g, " ")
+      const arr = Array.isArray(msgs) ? msgs : [String(msgs)]
+      for (const m of arr) lines.push(`${label} ${m}`)
+    }
+    if (lines.length) return lines.join("; ")
+  }
+
+  if (err instanceof Error && err.message) return err.message
+  if (typeof d.message === "string" && d.message) return d.message
+
+  return "An unexpected error occurred. Please try again."
+}
+
+/** Short heading to pair with {@link humanErrorMessage} in a boundary/card. */
+export function humanErrorTitle(err: unknown): string {
+  if (isRouteErrorResponse(err)) {
+    if (err.status === 404) return "Page not found"
+    return "Something went wrong"
+  }
+  return "Something went wrong"
+}