lists: measure a card, not the header, for cards-per-row

LEFT from any card of a grid's first row opened the menu drawer. The
cells-per-row estimate read the width of the first visible grid item,
but near the top that is the page header, which spans the whole width —
so it computed one card per row and treated every card as a row start.
Skip full-span items when estimating; row starts resolve correctly even
while the header is on screen.

app/src/main/java/net/jeena/jtubetv/ui/screens/list/VideoListScreen.kt

@@ -93,10 +93,15 @@ fun VideoListScreen(
 
     // Cards-per-row of the adaptive grid — LEFT from the first card of ANY row
     // must open the drawer (issue #7: "every time I'm all the way on the left").
+    // Measure a CARD, not the first visible item: the page header spans the full
+    // width, and reading its width made cards-per-row = 1 — every card near the
+    // top then thought it was a row start and opened the drawer.
     val cellsPerRow by remember {
         androidx.compose.runtime.derivedStateOf {
             val info = gridState.layoutInfo
-            val w = info.visibleItemsInfo.firstOrNull()?.size?.width ?: 0
+            val w = info.visibleItemsInfo
+                .firstOrNull { it.size.width < info.viewportSize.width }
+                ?.size?.width ?: 0
             if (w > 0) (info.viewportSize.width / w).coerceIn(1, 10) else 0
         }
     }