fix(634): stop the #616 guard from asserting an invariant the fix violates

Cold review finding. The #616 regression test looped over EVERY rerun-collection
request asserting pageNum === '0'. That was right when exactly one request was ever
issued, but since this branch the loader legitimately walks pageNum 1, 2, … to page to
completeness — so the assertion now describes something the correct code does not do.

It passes today only because the shared fixture's totalCount fits in a single page.
Raising that default would have failed the #616 test with a "picker requested page 1"
signal for what is proper paging, sending the next reader after a defect that isn't
there. Narrow it to the first request, which is the offset #616 actually cared about.

Also corrects the new comment's history: the `pageNum: 1` it describes is pre-#616,
not the previous commit.

web/src/screens/SchedulesScreen.test.tsx

@@ -180,10 +180,13 @@ describe('SchedulesScreen — load', () => {
     // clamped to 100 server-side that skipped the first 100 rows — so the picker showed nothing at
     // all for the ordinary case of <=100 rerun collections. Assert the offset, not just the URL
     // shape: `pageNum=1` here is a silent empty picker, never an error.
-    for (const request of rerunRequests) {
-      const pageNum = new URL(request.url, 'http://localhost').searchParams.get('pageNum');
-      expect(pageNum).toBe('0');
-    }
+    //
+    // Assert only the FIRST request. Since #634 the loader legitimately walks pageNum 1, 2, … to
+    // page to completeness, so "every request is page 0" is an invariant the CORRECT code violates.
+    // It holds today only because this fixture's totalCount fits in one page — raising that default
+    // would fail this test with a misleading "requested page 1" signal for what is proper paging.
+    const firstPageNum = new URL(rerunRequests[0].url, 'http://localhost').searchParams.get('pageNum');
+    expect(firstPageNum).toBe('0');
   });
 
   it('pages the rerun-collection picker to completeness when totalCount exceeds one page (#634)', async () => {

web/src/screens/SchedulesScreen.tsx

@@ -48,9 +48,9 @@ const DIRTY_PROMPT = 'You have unsaved schedule changes. Discard them?';
 // precedent — the client pages, the server stays bounded). Mirrors CollectionsScreen.enterReorder.
 //
 // `pageNum` is 0-BASED here and everywhere on /api/v1 (api.paging-zero-based): the first page is 0,
-// so the loop below starts its follow-up requests at 1. This call previously passed `pageNum: 1`,
-// which skipped the first page entirely and showed nothing at all for the normal case of <=100
-// rerun collections (ersatztv#616) — the same call site, one defect earlier.
+// so the loop below starts its follow-up requests at 1. Before ersatztv#616 this call site passed
+// `pageNum: 1`, which skipped the first page entirely and showed nothing at all for the ordinary
+// case of <=100 rerun collections — the same call site, one defect earlier.
 const RERUN_PAGE_SIZE = 100;
 
 async function loadAllRerunCollections(): Promise<RerunCollection[]> {