test(recipes): pilote le scroll dans le scénario 3 pages des sources

Le scénario ajouté supposait que l'IntersectionObserver se redéclenchait
tout seul avec une liste courte — faux : il ne se déclenche qu'à une
*transition* d'intersection. Les pages font maintenant 15 éléments (la
liste déborde son conteneur, la sentinelle démarre sous la ligne de
flottaison) et chaque page suivante est demandée via un
`scrollTo("bottom")` explicite, qui produit une vraie transition.

Avec l'ancien code bugué, la sentinelle stale rappelle « cursor-2 » au 2e
scroll : « Page 3 Item 1 » n'apparaît jamais et un curseur est redemandé
— les deux assertions échouent.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

apps/web/cypress/e2e/recipe-sources.feature

@@ -63,9 +63,11 @@ Feature: Browsing external recipe sources
     And browsing TheMealDB returns three pages, each addressed by its own cursor
     When I visit "/recettes"
     And I click the button "TheMealDB"
-    Then I should see the source item "Page One Dish"
-    And I should see the source item "Page Two Dish"
-    And I should see the source item "Page Three Dish"
+    Then I should see the source item "Page 1 Item 1"
+    When I scroll the source list to the bottom
+    Then I should see the source item "Page 2 Item 1"
+    When I scroll the source list to the bottom
+    Then I should see the source item "Page 3 Item 1"
     And no browse cursor should have been requested more than once
 
   Scenario: Offers a retry when loading the next page fails

apps/web/cypress/e2e/recipe-sources.ts

@@ -133,28 +133,39 @@ Given("browsing TheMealDB returns two pages of items", () => {
 });
 
 /**
- * Three real pages, each addressed by a distinct `cursor` value the mock
- * actually parses (not just "does the URL contain `cursor=`"). Records
- * every cursor it serves so the scenario can assert none was requested
- * twice — the tell-tale of the issue #38 loop, where a stale closure
- * re-requests the same page forever instead of advancing.
+ * Three full pages, each addressed by a distinct `cursor` value the mock
+ * actually parses (not just "does the URL contain `cursor=`"). Pages are
+ * deliberately large enough to overflow the list's own scroll container so
+ * the sentinel starts below the fold — each `scrollTo("bottom")` then
+ * produces a real IntersectionObserver transition, the only thing that
+ * makes the observer fire again. Records every cursor it serves so the
+ * scenario can assert none was requested twice — the tell-tale of the
+ * issue #38 loop, where a stale closure re-requests the same page forever
+ * instead of advancing.
  */
+const THREE_PAGE_SIZE = 15;
 const threePageCursorsRequested: string[] = [];
 
+function threePagePage(pageNo: number, nextCursor: string | null) {
+  return {
+    items: Array.from({ length: THREE_PAGE_SIZE }, (_, index) => ({
+      externalId: `p${pageNo}-${index}`,
+      title: `Page ${pageNo} Item ${index + 1}`,
+      picture: null,
+      url: `https://www.themealdb.com/meal/p${pageNo}-${index}`,
+      alreadyImported: false,
+      recipeId: null,
+    })),
+    nextCursor,
+  };
+}
+
 Given("browsing TheMealDB returns three pages, each addressed by its own cursor", () => {
   threePageCursorsRequested.length = 0;
-  const item = (externalId: string, title: string) => ({
-    externalId,
-    title,
-    picture: null,
-    url: `https://www.themealdb.com/meal/${externalId}`,
-    alreadyImported: false,
-    recipeId: null,
-  });
-  const pages: Record<string, { items: unknown[]; nextCursor: string | null }> = {
-    "": { items: [item("p1", "Page One Dish")], nextCursor: "cursor-2" },
-    "cursor-2": { items: [item("p2", "Page Two Dish")], nextCursor: "cursor-3" },
-    "cursor-3": { items: [item("p3", "Page Three Dish")], nextCursor: null },
+  const pages: Record<string, ReturnType<typeof threePagePage>> = {
+    "": threePagePage(1, "cursor-2"),
+    "cursor-2": threePagePage(2, "cursor-3"),
+    "cursor-3": threePagePage(3, null),
   };
   cy.intercept("GET", "**/sources/theMealDb/browse*", (req) => {
     const cursor = new URL(req.url).searchParams.get("cursor") ?? "";
@@ -163,15 +174,19 @@ Given("browsing TheMealDB returns three pages, each addressed by its own cursor"
   });
 });
 
+When("I scroll the source list to the bottom", () => {
+  cy.get(".source-items-column .recipe-table-wrap").scrollTo("bottom", {
+    ensureScrollable: false,
+  });
+  // IntersectionObserver callbacks are delivered on their own task, and the
+  // next page's fetch + merge then needs a render — give both a beat.
+  cy.wait(400);
+});
+
 Then("no browse cursor should have been requested more than once", () => {
-  // Let the panel settle (auto-scroll + one-page-ahead prefetch) before
-  // asserting. A looping IntersectionObserver would re-hit "" or "cursor-2"
-  // here; the latest-ref fix keeps each cursor to a single request.
-  cy.wait(600).then(() => {
   const seen = [...threePageCursorsRequested];
   expect(seen.length, `cursors requested: ${JSON.stringify(seen)}`).to.equal(new Set(seen).size);
 });
-});
 
 // The panel prefetches the next page as soon as page 1 is on screen (before
 // anyone's actually waited on it), so the *first* request for it is that