feat: multiple test patterns in testpattern node

V210.hpp: add fill_colorbars, fill_ire_ramp, fill_black, fill_white.
Shared fill_solid helper stamps the first line across all rows via
memcpy. Generic write_palette_line template handles both SMPTE and
IRE bar palettes. fill_frame kept as a backward-compat alias.

testpattern/main.cpp: read "pattern" from node config and dispatch
to the appropriate fill function (bars/ire/black/white).

build_graph: pass {"pattern","bars"} to testpattern node params.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

shared/V210.hpp

@@ -2,6 +2,7 @@
 #include <array>
 #include <cstddef>
 #include <cstdint>
+#include <cstring>
 
 namespace dmf::v210 {
 
@@ -82,12 +83,67 @@ inline void write_bar_line(uint8_t* line, int width, uint32_t /*stride*/)
     }
 }
 
-// Fill an entire frame buffer with color bars.
+// Write one horizontal line of an arbitrary bar palette.
+template<std::size_t N>
+inline void write_palette_line(uint8_t* line, int width, const std::array<Color, N>& palette)
+{
+    const int n = static_cast<int>(N);
+    const int blocks = width / 6;
+    for (int b = 0; b < blocks; b++) {
+        int x = b * 6;
+        auto color = [&](int px) -> const Color& {
+            return palette[static_cast<std::size_t>(px * n / width)];
+        };
+        const Color& c01 = color(x);
+        const Color& c23 = color(x + 2);
+        const Color& c45 = color(x + 4);
+        pack_block(line + b * 16,
+            c01, c01.y, color(x+1).y,
+            c23, c23.y, color(x+3).y,
+            c45, c45.y, color(x+5).y);
+    }
+}
+
+// Fill a frame with a solid color.
+inline void fill_solid(uint8_t* buf, int width, int height, uint32_t stride, Color c)
+{
+    const int blocks = width / 6;
+    for (int b = 0; b < blocks; b++)
+        pack_block(buf + b * 16, c, c.y, c.y, c, c.y, c.y, c, c.y, c.y);
+    for (int y = 1; y < height; y++)
+        std::memcpy(buf + static_cast<ptrdiff_t>(y) * stride, buf, blocks * 16);
+}
+
+// SMPTE 75% color bars.
+inline void fill_colorbars(uint8_t* buf, int width, int height, uint32_t stride)
+{
+    for (int y = 0; y < height; y++)
+        write_palette_line(buf + static_cast<ptrdiff_t>(y) * stride, width, SMPTE_BARS);
+}
+
+// IRE 11-step greyscale ramp.
+inline void fill_ire_ramp(uint8_t* buf, int width, int height, uint32_t stride)
+{
+    for (int y = 0; y < height; y++)
+        write_palette_line(buf + static_cast<ptrdiff_t>(y) * stride, width, IRE_BARS);
+}
+
+// 10-bit limited black  (Y=64,  Cb=Cr=512).
+inline void fill_black(uint8_t* buf, int width, int height, uint32_t stride)
+{
+    fill_solid(buf, width, height, stride, {64, 512, 512});
+}
+
+// 10-bit limited white  (Y=940, Cb=Cr=512).
+inline void fill_white(uint8_t* buf, int width, int height, uint32_t stride)
+{
+    fill_solid(buf, width, height, stride, {940, 512, 512});
+}
+
+// Kept for backward compatibility.
 inline void fill_frame(uint8_t* buf, int width, int height, uint32_t stride)
 {
-    for (int y = 0; y < height; y++) {
-        write_bar_line(buf + static_cast<ptrdiff_t>(y) * stride, width, stride);
-    }
+    fill_colorbars(buf, width, height, stride);
 }
 
 inline void UYVYtoV210(uint8_t* src_buf, uint8_t* dst_buf, int width, int height, uint32_t src_stride, uint32_t dst_stride)