feat(downloads): animate priority reordering

Rename the package disclosure option to a general animations switch and use it for both disclosure and priority-order motion. Keep previously visible virtual rows mounted during reorders, animate measured start and target positions for 1.5 seconds, and cancel all motion immediately when the setting is disabled. Extend the isolated renderer fixture so enabled and disabled behavior can be measured without touching user download state.

tests/settings-view.test.tsx

@@ -501,7 +501,7 @@ describe("settings views", () => {
     expect(settingsCss).toMatch(/\.settings-select\.is-open\s+\.settings-select-options\s*\{[^}]*opacity:\s*1[^}]*transform:\s*translateY\(0\)/s);
   });
 
-  it("offers a general switch for package expand and collapse motion", () => {
+  it("offers one general switch for interface animations", () => {
     const form = buildSettingsFormViewModel({
       settings: { ...createRendererSettings(defaultSettings()), archivePasswordList: "", notifyUrl: "" },
       section: "allgemein",
@@ -514,7 +514,7 @@ describe("settings views", () => {
     expect(animation).toEqual({
       id: "animatePackageDisclosure",
       kind: "switch",
-      label: "Paket-Ein-/Ausklappen animieren",
+      label: "Animationen",
       value: true
     });
   });