[Feat] (MG_Backend/DirectVulkan): wire glPolygonMode and glColorMaski into pipeline creation

Consume the polygon mode and per-draw-buffer color write masks that the
frontend already tracks, with runtime fallback for the device features
they require.

glPolygonMode:
- Add ConvertPolygonModeToVkEnum (GL_FILL/LINE/POINT -> VkPolygonMode).
- Thread a polygonMode field through PipelineCreatePayload, fold it into
  the pipeline cache hash (distinct modes need distinct pipelines), and
  apply it in PipelineFactory instead of the hardcoded VK_POLYGON_MODE_FILL.
- LINE/POINT require the fillModeNonSolid device feature: detect and
  enable it at device creation, cache m_fillModeNonSolidFeatureEnabled,
  and fall back to FILL at pipeline-build time when it is absent.

glColorMaski:
- The per-attachment color-blend loop now reads GetColorMaskIndexed(i)
  instead of the broadcast GetColorMask(), so each draw buffer gets its
  own write mask (already covered by the pipeline hash).
- Divergent per-attachment masks require independentBlend: cache
  m_independentBlendFeatureEnabled (was enabled but never recorded) and
  fall back to draw buffer 0's mask for every attachment when it is absent.

The internal depth-mipmap utility pipeline keeps VK_POLYGON_MODE_FILL (not
GL-driven). Library builds clean; full SanityTest sweep green (30/30).

MobileGL/MG_Util/Converters/MGToVk/RenderStateEnumConverter.cpp

@@ -31,6 +31,20 @@ namespace MobileGL {
             }
         }
 
+        VkPolygonMode ConvertPolygonModeToVkEnum(GLenum mode) {
+            switch (mode) {
+            case GL_FILL:
+                return VK_POLYGON_MODE_FILL;
+            case GL_LINE:
+                return VK_POLYGON_MODE_LINE;
+            case GL_POINT:
+                return VK_POLYGON_MODE_POINT;
+            default:
+                MGLOG_W("Unrecognized polygon mode");
+                return VK_POLYGON_MODE_FILL;
+            }
+        }
+
         VkCullModeFlags ConvertCullFaceModeToVkEnum(CullFaceMode v, Bool invertClockwise) {
             switch (v) {
             case CullFaceMode::Front:

MobileGL/MG_Util/Converters/MGToVk/RenderStateEnumConverter.h

@@ -13,6 +13,10 @@
 namespace MobileGL {
     namespace MG_Util {
         VkPrimitiveTopology ConvertPrimitiveModeToVkEnum(GLenum mode);
+        // Maps GL_FILL/GL_LINE/GL_POINT to the matching VkPolygonMode. LINE/POINT require the
+        // fillModeNonSolid device feature; the caller is responsible for falling back to FILL when
+        // that feature is unavailable.
+        VkPolygonMode ConvertPolygonModeToVkEnum(GLenum mode);
         VkCullModeFlags ConvertCullFaceModeToVkEnum(CullFaceMode value, Bool invertClockwise = false);
         VkLogicOp ConvertLogicOperationToVkEnum(LogicOperation value);
         VkCompareOp ConvertDepthTestFuncToVkEnum(DepthTestFunc value);