feat(demo): make return, data-quality and knowledge flows demo-legible

Fixes a real honesty bug in Knowledge.tsx (body copy named "RAGcore" while
the active provider is the demo one) and a second real bug discovered
while fixing it: the brief's suggested Dutch questions would silently
return "insufficient evidence" against the English-only demo knowledge
base -- verified empirically and fixed by keeping suggested questions in
English. The return flow now pre-fills the odometer-regression scenario's
suspicious reading instead of asking a visitor to invent one, and links
to automation/audit after committing. Data-quality issues get a shared
plain-language "what's wrong / why it matters" explainer per rule type,
a post-resolution confirmation with audit/vehicle links, and a "demo
scenario's only" list filter. Also fixes a real async race where the
odometer pre-fill could clobber text a visitor had already started typing.

frontend/src/pages/BookingDetail.tsx

@@ -1,7 +1,8 @@
 import { useCallback, useEffect, useState } from "react";
 import { Link, useParams } from "react-router-dom";
 import { api } from "../api/client";
-import type { Booking, RegisterReturnResult } from "../api/types";
+import type { Booking, RegisterReturnResult, VehicleDetail } from "../api/types";
+import { useDemoManifest } from "../context/DemoManifestContext";
 import { StatusBadge } from "../components/Badge";
 import { ReturnForm, ReturnResultPanel } from "../components/ReturnForm";
 import { Icon } from "../components/Icons";
@@ -9,9 +10,11 @@ import { ErrorState, LoadingState, PageHeader } from "../components/PageChrome";
 
 export function BookingDetail() {
   const { publicRef } = useParams<{ publicRef: string }>();
+  const { manifest } = useDemoManifest();
   const [booking, setBooking] = useState<Booking | null>(null);
   const [error, setError] = useState<string | null>(null);
   const [returnResult, setReturnResult] = useState<RegisterReturnResult | null>(null);
+  const [canonicalOdometerKm, setCanonicalOdometerKm] = useState<number | null>(null);
 
   const load = useCallback(() => {
     if (!publicRef) return;
@@ -28,6 +31,21 @@ export function BookingDetail() {
     load();
   }, [load]);
 
+  // The odometer-regression demo scenario supplies its own suspicious reading (per the
+  // brief: never ask a demo visitor to invent one) -- only fetched for that one known
+  // scenario booking, not for every return.
+  const isReturnAnomalyScenario =
+    manifest?.scenarios.find((s) => s.id === "return-anomaly")?.start_path === `/bookings/${publicRef}`;
+
+  useEffect(() => {
+    setCanonicalOdometerKm(null);
+    if (!isReturnAnomalyScenario || !booking) return;
+    api
+      .get<VehicleDetail>(`/api/v1/vehicles/${booking.vehicle_ref}`)
+      .then((vehicle) => setCanonicalOdometerKm(vehicle.odometer_km))
+      .catch(() => setCanonicalOdometerKm(null));
+  }, [isReturnAnomalyScenario, booking]);
+
   function handleRegistered(result: RegisterReturnResult) {
     setReturnResult(result);
     load();
@@ -50,9 +68,28 @@ export function BookingDetail() {
         <div><dt>Requirements complete</dt><dd>{booking.requirements_complete ? "Yes" : "No"}</dd></div>
       </dl></section>
 
+      {isReturnAnomalyScenario && !returnResult && canonicalOdometerKm !== null && (
+        <section className="record-surface scenario-callout" aria-label="Demo scenario">
+          <Icon name="spark" />
+          <div>
+            <strong>Demonstratiescenario: afwijkende kilometerstand</strong>
+            <p>
+              Dit voertuig staat momenteel op <strong>{canonicalOdometerKm.toLocaleString("en-GB")} km</strong>.
+              Het onderstaande formulier is vooraf ingevuld met een retourstand die daaronder
+              ligt — een teken van een foutieve invoer of een verwisseld voertuig. Bevestig de
+              retour om te zien hoe MobilityOps dit detecteert en afhandelt.
+            </p>
+          </div>
+        </section>
+      )}
+
       {returnResult && <ReturnResultPanel result={returnResult} />}
       {!returnResult && booking.status === "active" && (
-        <ReturnForm bookingRef={booking.public_ref} onRegistered={handleRegistered} />
+        <ReturnForm
+          bookingRef={booking.public_ref}
+          onRegistered={handleRegistered}
+          suggestedOdometerKm={isReturnAnomalyScenario && canonicalOdometerKm !== null ? Math.max(0, canonicalOdometerKm - 50) : undefined}
+        />
       )}
     </div>
   );