fix(svod2): при поиске/фильтре на глубине total берётся из запасного offset=0, а не из долгого ответа за концом списка

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

web/src/pages/Svod2Page/useSvod2Pages.js

@@ -17,6 +17,7 @@ import {
 	getVisiblePage,
 	getWindowPages,
 	getWindowRange,
+	shouldFetchFirstPageFallback,
 	shouldRefine,
 	svod2PagingReducer,
 } from './svod2Paging';
@@ -59,7 +60,7 @@ export function useSvod2Pages({ sheet, year, orgIds, queryKey, search, columnFil
 		if (mountedRef.current) setState(next);
 	}, []);
 
-	const fetchPage = useCallback(async (ctx, pageIndex) => {
+	const fetchPage = useCallback(async (ctx, pageIndex, signal = ctx.controller.signal) => {
 		ctx.inflight.add(pageIndex);
 		try {
 			const response = await SummaryApi.getSvod2Page(
@@ -71,7 +72,7 @@ export function useSvod2Pages({ sheet, year, orgIds, queryKey, search, columnFil
 					columnFilters: ctx.columnFilters,
 					offset: pageIndex * PAGE_SIZE,
 				}),
-				{ signal: ctx.controller.signal },
+				{ signal },
 			);
 			const rows = response.result || [];
 			return { rows, total: response.total ?? rows.length };
@@ -138,14 +139,43 @@ export function useSvod2Pages({ sheet, year, orgIds, queryKey, search, columnFil
 
 			const loadPages = async () => {
 				try {
-					const first = await fetchPage(ctx, candidate);
+					// Страница по прокрутке и (на глубине) запасная offset=0 летят параллельно: если страница по прокрутке
+					// за концом нового списка, сервер отвечает на неё долго и без строк, а страница 0 уже даёт total.
+					const candidateController = new AbortController();
+					const zeroController = new AbortController();
+					const abortRequests = () => {
+						candidateController.abort();
+						zeroController.abort();
+					};
+					ctx.controller.signal.addEventListener('abort', abortRequests);
+					const settle = (request, index) =>
+						request.then(
+							(result) => ({ result, index }),
+							(error) => ({ error, index }),
+						);
+					const candidateRequest = settle(fetchPage(ctx, candidate, candidateController.signal), candidate);
+					const zeroRequest = candidate > 0 ? settle(fetchPage(ctx, 0, zeroController.signal), 0) : null;
+					let answer = zeroRequest ? await Promise.race([candidateRequest, zeroRequest]) : await candidateRequest;
+					if (
+						answer.index === 0 &&
+						candidate > 0 &&
+						!answer.error &&
+						shouldFetchFirstPageFallback({ candidate, total: answer.result.total })
+					) {
+						candidateController.abort();
+					} else {
+						zeroController.abort();
+						answer = await candidateRequest;
+						if (answer.error) throw answer.error;
+					}
 					if (ctx.controller.signal.aborted) return;
+					const first = answer.result;
 					const { total } = first;
 					const pages = getWindowFor(total);
 					const pageCount = getPageCount(total);
 					let cache = new Map();
-					if (total === 0 || candidate < pageCount) {
+					if (total === 0 || answer.index < pageCount) {
-						const pageIndex = total === 0 ? 0 : candidate;
+						const pageIndex = total === 0 ? 0 : answer.index;
 						dispatch({ type: 'page', sheet: sheetKey, generation, pageIndex, rows: first.rows, total, keepPages: pages });
 						cache = stateRef.current[sheetKey].pages;
 					}