docs(stalker): record series position compatibility

libs/shared/interfaces/src/lib/stalker-item.normalizer.spec.ts

@@ -23,6 +23,19 @@ describe('extractStalkerItemType', () => {
             })
         ).toBe('live');
     });
+
+    it.each([true, 1, '1'] as const)(
+        'treats is_series=%p as a series item',
+        (isSeries) => {
+            expect(
+                extractStalkerItemType({
+                    id: '50001',
+                    title: 'Portal Series',
+                    is_series: isSeries,
+                })
+            ).toBe('series');
+        }
+    );
 });
 
 describe('isStalkerRadioItem', () => {

libs/shared/interfaces/src/lib/stalker-item.normalizer.ts

@@ -50,7 +50,7 @@ export function extractStalkerItemPoster(
  * Determine the normalised activity type of a Stalker item.
  *
  * - `itv` / `live` / radio → `'live'`
- * - `series` or `is_series` truthy → `'series'`
+ * - `series` or `is_series` equal to `true`, `1`, or `'1'` → `'series'`
  * - everything else → `'movie'`
  */
 export function extractStalkerItemType(