vf_cuda_grid: add main_with_strip layout (5 cells, info strip без input)

Layout 1280x720 output:
  cell 0: main 960×540 = 16:9 (no stretch при camera 1920x1080)
  cells 1-3: 320×180 preview right column (16:9 native)
  cell 4: 1280×180 info strip (full width bottom)

Use case: cell 4 без input pad → blank background, overlay через icon/text
overlays (Grafana, чат, status). Pipeline нужен 5й input source (lavfi
color=black:size=1280x180:rate=25) для filter framesync.

Решает user complaint: main_plus_preview cell 0 = 2/3 width × full height
= 853×720 = 1.18:1 → 16:9 camera стretching по высоте. main_with_strip
cell 0 = exact 16:9.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

libavfilter/vf_cuda_grid.c

@@ -182,6 +182,19 @@ static const LayoutTemplate layouts[] = {
         "panoramic", 1,
         { {0.0f, 0.0f, 1.0f, 1.0f} }
     },
+    {
+        /* Main 16:9 (960×540 при 1280×720 output) + 3 preview right + bottom strip.
+         * cell 4 = info strip (1280×180), без input pad → blank background для
+         * browser overlays / text / chat. Все cells 16:9 native — no stretch. */
+        "main_with_strip", 5,
+        {
+            {0.0f,  0.0f,  0.75f, 0.75f},   /* 0: main 16:9 */
+            {0.75f, 0.0f,  0.25f, 0.25f},   /* 1: preview top */
+            {0.75f, 0.25f, 0.25f, 0.25f},   /* 2: preview mid */
+            {0.75f, 0.5f,  0.25f, 0.25f},   /* 3: preview bot */
+            {0.0f,  0.75f, 1.0f,  0.25f},   /* 4: info strip — для overlays */
+        }
+    },
 };
 
 static const LayoutTemplate *find_layout(const char *name)