fix(site-finder): remount analysis tree on cad change (#2445-B4)

AnalysisPageContent не имел key, привязанного к cad, поэтому клиентская
навигация между участками под тем же [cad]-роутом переиспользовала инстанс —
результат useCreateConcept §7, выбранный конкурент/фильтры §3 и thread
ChatPanel утекали от предыдущего участка. key={cad} форсит чистый remount;
cad-keyed TanStack-данные не затронуты (перечитываются из кэша, без refetch-
водопада). Паттерн уже используется в compare/page.tsx.

Усилен regression-тест 2: rerender() с изменённым key (пиннит сам механизм)
вместо unmount()+render() (сбрасывал бы state безусловно).

Refs #2445

frontend/src/app/site-finder/analysis/[cad]/__tests__/AnalysisPageContent.remount.test.tsx

@@ -0,0 +1,172 @@
+import { fireEvent, render, screen } from "@testing-library/react";
+import { QueryClient, QueryClientProvider } from "@tanstack/react-query";
+import { describe, expect, it, vi } from "vitest";
+
+import { AnalysisPageContent } from "../AnalysisPageContent";
+
+// ── Regression test: epic #2445 item B4 ──────────────────────────────────────
+//
+// Bug: AnalysisPageContent (and its §7 Section7Concept child) was rendered
+// without a React `key` tied to `cad`. Client-side nav between two different
+// parcels under the SAME /site-finder/analysis/[cad] route template (e.g.
+// RecentParcels / CompareTable → plain next/link to a different cad) reused
+// the same component instance — instance-local state (§7's useCreateConcept
+// mutation result, which has no cache key: it lives only in
+// concept.data/isSuccess/isError) kept showing the OLD parcel's computed
+// concept until the user manually re-ran it.
+//
+// Fix: page.tsx now renders <AnalysisPageContent key={cad} cad={cad} /> so a
+// parcel change forces a clean remount. This test exercises that exact
+// pattern (rendering AnalysisPageContent keyed by cad, same as page.tsx) and
+// asserts:
+//   1. Same cad, re-render → local state in a §7-like child is PRESERVED
+//      (normal interaction, e.g. horizon change, must not lose progress).
+//   2. Different cad → local state RESETS (remount), instead of leaking the
+//      previous parcel's concept into the new parcel's view.
+//
+// The real §7Concept/useCreateConcept + all sibling sections pull in Leaflet/
+// ECharts/TanStack Query fetches — irrelevant to the remount contract under
+// test — so every section is mocked with a light stub. The Section7Concept
+// stub mirrors the real bug shape: a plain useState "concept result" with NO
+// cad-keyed cache, set via a button click (stand-in for the mutation firing).
+
+vi.mock("@/lib/site-finder-api", async () => {
+  const actual = await vi.importActual<typeof import("@/lib/site-finder-api")>(
+    "@/lib/site-finder-api",
+  );
+  return {
+    ...actual,
+    useParcelAnalyzeQuery: (cad: string) => ({
+      data: { district: null, egrn: null, gate_verdict: null, cad },
+      isLoading: false,
+      isFetching: false,
+      error: null,
+    }),
+  };
+});
+
+vi.mock("@/components/site-finder/ChatDock", () => ({
+  ChatDock: () => null,
+}));
+vi.mock("@/components/site-finder/GateVerdictBanner", () => ({
+  GateVerdictBanner: () => null,
+}));
+vi.mock("@/components/site-finder/HorizonSelector", () => ({
+  HorizonSelector: () => null,
+}));
+vi.mock("@/components/site-finder/analysis/Section1ParcelInfo", () => ({
+  Section1ParcelInfo: () => null,
+}));
+vi.mock("@/components/site-finder/analysis/Section2NetworksUtilities", () => ({
+  Section2NetworksUtilities: () => null,
+}));
+vi.mock(
+  "@/components/site-finder/analysis/Section3SettingsAndCompetitors",
+  () => ({ Section3SettingsAndCompetitors: () => null }),
+);
+vi.mock("@/components/site-finder/analysis/Section4Estimate", () => ({
+  Section4Estimate: () => null,
+}));
+vi.mock("@/components/site-finder/analysis/Section5Atmosphere", () => ({
+  Section5Atmosphere: () => null,
+}));
+vi.mock("@/components/site-finder/analysis/Section6Forecast", () => ({
+  Section6Forecast: () => null,
+}));
+vi.mock("@/components/site-finder/analysis/SectionAlternatives", () => ({
+  SectionAlternatives: () => null,
+}));
+
+// Stub §7: a plain useState "concept" with no cad-keyed cache — the exact
+// shape of the real useCreateConcept()-backed bug. A button click simulates
+// the mutation firing and settling.
+vi.mock("@/components/site-finder/analysis/Section7Concept", () => {
+  const React = require("react") as typeof import("react");
+  return {
+    Section7Concept: () => {
+      const [concept, setConcept] = React.useState<string | null>(null);
+      return (
+        <div>
+          <button type="button" onClick={() => setConcept("computed-concept")}>
+            Сгенерировать концепцию
+          </button>
+          <div data-testid="concept-state">{concept ?? "empty"}</div>
+        </div>
+      );
+    },
+  };
+});
+
+// AnalysisPageContent calls useQueryClient() directly (horizon-change
+// invalidation) even though useParcelAnalyzeQuery is mocked above, so every
+// render needs a real QueryClientProvider ancestor.
+function renderKeyed(cad: string) {
+  const client = new QueryClient();
+  return render(
+    <QueryClientProvider client={client}>
+      <AnalysisPageContent key={cad} cad={cad} />
+    </QueryClientProvider>,
+  );
+}
+
+describe("AnalysisPageContent — key={cad} remount contract (#2445 B4)", () => {
+  it("preserves §7-like local state across a re-render with the SAME cad", () => {
+    const client = new QueryClient();
+    const cad = "66:41:0204016:10";
+    const { rerender } = render(
+      <QueryClientProvider client={client}>
+        <AnalysisPageContent key={cad} cad={cad} />
+      </QueryClientProvider>,
+    );
+
+    fireEvent.click(
+      screen.getByRole("button", { name: "Сгенерировать концепцию" }),
+    );
+    expect(screen.getByTestId("concept-state").textContent).toBe(
+      "computed-concept",
+    );
+
+    // Same cad → same key → React must NOT remount; in-progress state stays
+    // (e.g. a horizon change re-renders the same tree — must not lose it).
+    rerender(
+      <QueryClientProvider client={client}>
+        <AnalysisPageContent key={cad} cad={cad} />
+      </QueryClientProvider>,
+    );
+    expect(screen.getByTestId("concept-state").textContent).toBe(
+      "computed-concept",
+    );
+  });
+
+  it("resets §7-like local state when navigating to a DIFFERENT cad", () => {
+    // Single render tree that we rerender() with a CHANGED key — this pins the
+    // `key={cad}` mechanism itself. A fresh unmount()+render() would reset state
+    // unconditionally (even with no key), so it would pass on a reverted fix and
+    // wouldn't guard the regression. With rerender() + changed key, React keeps
+    // the tree mounted and only remounts because the key differs — exactly what
+    // page.tsx's `key={cad}` does on client-side nav. Drop the key in page.tsx
+    // and the OLD instance is reused, leaking "computed-concept" → this fails.
+    const client = new QueryClient();
+    const { rerender } = render(
+      <QueryClientProvider client={client}>
+        <AnalysisPageContent key="66:41:0204016:10" cad="66:41:0204016:10" />
+      </QueryClientProvider>,
+    );
+
+    fireEvent.click(
+      screen.getByRole("button", { name: "Сгенерировать концепцию" }),
+    );
+    expect(screen.getByTestId("concept-state").textContent).toBe(
+      "computed-concept",
+    );
+
+    // Client-side nav to a different parcel: same tree position, different key.
+    rerender(
+      <QueryClientProvider client={client}>
+        <AnalysisPageContent key="66:41:0702033:20" cad="66:41:0702033:20" />
+      </QueryClientProvider>,
+    );
+
+    expect(screen.getByTestId("concept-state").textContent).toBe("empty");
+  });
+});

frontend/src/app/site-finder/analysis/[cad]/page.tsx

@@ -47,7 +47,19 @@ export default async function AnalysisPage({ params }: PageProps) {
         </div>
       }
     >
-      <AnalysisPageContent cad={cad} />
+      {/* key={cad}: client-side nav between two parcels under this same route
+          template (RecentParcels / CompareTable link straight to /analysis/
+          CAD_B) does NOT remount by default — App Router reuses the instance,
+          so instance-local state (§7's useCreateConcept mutation result +
+          autoRun refs, §3's selected competitor/filters, the chat thread in
+          ChatDock/ChatPanel) would keep showing the OLD parcel's values until
+          manually re-run/reselected. Forcing a remount on cad change resets
+          all of it cleanly. Queries under this tree (parcel-analyze,
+          parcel-forecast, …) are TanStack Query and keyed by cad, so a
+          remount just re-subscribes to the (already cached) query result —
+          no extra fetch waterfall. Same cad → same key → React does NOT
+          remount (a normal re-render, e.g. horizon change, keeps state). */}
+      <AnalysisPageContent key={cad} cad={cad} />
     </Suspense>
   );
 }