feat(stock): beforeunload warning when pricing draft is dirty

src/app/(app)/stock/page.test.tsx

@@ -428,4 +428,25 @@ describe("StockListPage", () => {
       expect(await screen.findByText("Missing both")).toBeInTheDocument();
     });
   });
+
+  describe("Stock list — beforeunload while dirty", () => {
+    beforeEach(() => {
+      _resetState();
+      _state.items = [
+        { id: "aaaaaaaaaaaaaaa", sku: "B-001", name: "M10 Hex Bolt", selling_price: 0, cost_price: 0, markup: 0, current_qty: 5, min_qty: 0, is_active: true, supplier: "" },
+      ];
+      window.localStorage.clear();
+    });
+    afterEach(() => cleanup());
+
+    it("registers a beforeunload listener when there are dirty rows", async () => {
+      const addSpy = vi.spyOn(window, "addEventListener");
+      render(<Page />);
+      await screen.findByText("M10 Hex Bolt"); // wait for items
+      fireEvent.click(screen.getByRole("button", { name: /Edit pricing/i }));
+      const costInput = await screen.findByLabelText(/Cost for B-001/i);
+      fireEvent.change(costInput, { target: { value: "5" } });
+      expect(addSpy).toHaveBeenCalledWith("beforeunload", expect.any(Function));
+    });
+  });
 });

src/app/(app)/stock/page.tsx

@@ -177,6 +177,23 @@ export default function StockListPage() {
     }
   }, [pricingDraft]);
 
+  // Warn the operator before they navigate away with unsaved pricing
+  // changes. Only registered when edit mode is on AND there's actually
+  // something in the draft — the bar already gates the apply button
+  // on the same condition, so a Cmd-W / tab close here would silently
+  // lose the work otherwise.
+  useEffect(() => {
+    if (typeof window === "undefined") return;
+    const isDirty = Object.keys(pricingDraft).length > 0 && editPricing;
+    if (!isDirty) return;
+    const handler = (e: BeforeUnloadEvent) => {
+      e.preventDefault();
+      e.returnValue = "";
+    };
+    window.addEventListener("beforeunload", handler);
+    return () => window.removeEventListener("beforeunload", handler);
+  }, [pricingDraft, editPricing]);
+
   // Debounce the search input → 250ms after the last keystroke. Same
   // pattern as /orders and /quotes — the operator is hunting for a
   // match, not paging through.