fix: use 1:1 min aspect on landscape, scrollbar-gutter to prevent flicker

- minAspect=1:1 (square) on landscape containers, 3:4 on portrait
- scrollbar-gutter:stable on grid prevents scrollbar feedback loop

src/app/call.ts

@@ -122,14 +122,14 @@ const buildUniformRow = (
   containerWidth: number,
   containerHeight: number,
   rowCount: number,
+  minAspect: number,
 ): TileRow => {
   const gap = TILE_GAP
   const availableHeight = containerHeight - (rowCount - 1) * gap
   const rowHeight = availableHeight / rowCount
   const tileWidth = (containerWidth - (columnCount - 1) * gap) / columnCount
   const fillAspect = tileWidth / rowHeight
-  // Cap at 16:9 to avoid horizontally stretching video (review feedback)
-  const aspectRatio = Math.max(TILE_ASPECT_PORTRAIT, Math.min(TILE_ASPECT_LANDSCAPE, fillAspect))
+  const aspectRatio = Math.max(minAspect, Math.min(TILE_ASPECT_LANDSCAPE, fillAspect))
   const tileHeight = tileWidth / aspectRatio
   return {columnCount, tileWidth, tileHeight, aspectRatio}
 }
@@ -151,6 +151,7 @@ const buildMixedCandidate = (
   columnCount: number,
   containerWidth: number,
   containerHeight: number,
+  minAspect: number,
 ): AdaptiveTileGrid | undefined => {
   const gap = TILE_GAP
   const fullRowCount = Math.floor(tileCount / columnCount)
@@ -163,10 +164,9 @@ const buildMixedCandidate = (
   const tileWidthLast = (containerWidth - (remainder - 1) * gap) / remainder
   if (tileWidthLast <= 0) return undefined
 
-  // Find a common height that fits both row types and container
   const maxPossibleHeight = Math.min(
-    tileWidthFull / TILE_ASPECT_PORTRAIT,
-    tileWidthLast / TILE_ASPECT_PORTRAIT,
+    tileWidthFull / minAspect,
+    tileWidthLast / minAspect,
     (containerHeight - (totalRowCount - 1) * gap) / totalRowCount,
   )
 
@@ -234,6 +234,11 @@ export const computeAdaptiveGrid = (
 ): AdaptiveTileGrid | undefined => {
   if (tileCount <= 0 || containerWidth <= 0 || containerHeight <= 0) return undefined
 
+  // On landscape viewports, bound tiles at 1:1 (square) so they don't
+  // become tall and narrow. On portrait viewports, allow 3:4 so more
+  // tiles fit on a phone screen.
+  const minAspect = containerWidth > containerHeight ? 1 : TILE_ASPECT_PORTRAIT
+
   let best: AdaptiveTileGrid | undefined
   let bestScore: LayoutScore | undefined
 
@@ -246,7 +251,13 @@ export const computeAdaptiveGrid = (
 
     if (remainder === 0) {
       // Uniform layout — all rows identical
-      const row = buildUniformRow(columnCount, containerWidth, containerHeight, totalRowCount)
+      const row = buildUniformRow(
+        columnCount,
+        containerWidth,
+        containerHeight,
+        totalRowCount,
+        minAspect,
+      )
       const totalHeight = totalRowCount * row.tileHeight + (totalRowCount - 1) * TILE_GAP
       const totalWidth = columnCount * row.tileWidth + (columnCount - 1) * TILE_GAP
       const rows: TileRow[] = []
@@ -261,7 +272,13 @@ export const computeAdaptiveGrid = (
       }
     } else {
       // Mixed layout — last row has fewer tiles, make them wider
-      candidate = buildMixedCandidate(tileCount, columnCount, containerWidth, containerHeight)
+      candidate = buildMixedCandidate(
+        tileCount,
+        columnCount,
+        containerWidth,
+        containerHeight,
+        minAspect,
+      )
     }
 
     if (!candidate) continue

src/app/components/VideoCallContent.svelte

@@ -270,7 +270,7 @@
       <div
         bind:clientWidth={gridWidth}
         bind:clientHeight={gridHeight}
-        class="min-h-0 flex-1 overflow-y-auto">
+        class="min-h-0 flex-1 overflow-y-auto [scrollbar-gutter:stable]">
         {#if tileGrid}
           <div class="flex flex-col items-center gap-2">
             {#each tileGrid.rows as row, rowIndex}