[Refactor] (Magma): route every frontend read through MGB_CTX - 164 arrow sites sed'd, 49 non-arrow lines converted (43 asserts keep their meaning as MGB_CTX_LIVE); pull build byte-identical

- Every MG_State::pGLContext-> in the seven DirectVulkan TUs becomes MGB_CTX->
  (DirectVulkan.cpp 12, BackendObject_DirectVulkan.cpp 2, UniformManager.cpp 14,
  VkClearManager.cpp 1, VkRenderPassManager.cpp 3, VkTextureManager.cpp 2,
  VulkanRenderer.cpp 130 occurrences on 127 lines); each TU includes
  <MG_Pipe/PipeInputsSwitch.h> right after its MG_State/GLState/Core.h include
  (VkRenderPassManager.cpp after its include block, it never included Core.h).
- The 43 MOBILEGL_ASSERT(pGLContext) / (pGLContext != nullptr) lines become
  MOBILEGL_ASSERT(MGB_CTX_LIVE, ...): identical in every INFO build (the macro is
  empty there) and still a null-context assert in a DEBUG build.
- The six code-bearing guards are like-for-like pointer tests in the pull arm:
  if (MGB_CTX_LIVE) at the two InvalidateCompileEnv sites, MGB_CTX_LIVE in the
  XFB query counter condition and the ternary that snapshots the paused-primitive
  counter, !MGB_CTX_LIVE in BeginXfbCaptureForDraw, MGB_CTX_LIVE && in the
  provoking-vertex resolve. No semantic rewrite: under push MGB_CTX_LIVE is simply
  "a context exists", the real meaning of these guards is P2's business.
- VertexInputStateFactory.h's comment stops naming pGLContext so purity gate C
  (grep -rc pGLContext MobileGL/MG_Backend/DirectVulkan) reads 0 in every file.
- The 12 SyncPersistentMappedRange and 3 SyncGpuWrites sites of the D10 table are
  untouched; PipeStats AddCalls literals unchanged.
- Proof on the pull build (Release/INFO, LTO off, vs feat/disaggregated@087685d1):
  symbol_report --threshold 0 -> 27799 symbols, 0 added / 0 removed / 0 resized /
  0 renamed, .text 10792579 -> 10792579 (+0); nm --defined-only name set identical;
  ctest -N name set identical (2334); unit 1466/1466; DirectVulkan integration lane
  427/427 on lavapipe (two ArmedWhenTheEnvironmentPinsItOn entries flake under -j 4
  exactly as on the baseline and pass serially). The push build compiles and links.

MobileGL/MG_Backend/DirectVulkan/BackendObject_DirectVulkan.cpp

@@ -12,6 +12,7 @@
 #include "SubgroupSupportPolicy.h"
 #include "MG_State/GLState/FramebufferState/FramebufferObject.h"
 #include "MG_State/GLState/Core.h"
+#include <MG_Pipe/PipeInputsSwitch.h>
 #include "MG_State/GLState/TextureState/TextureState.h"
 #include "MG_Util/Classifiers/TextureEnumClassifier.h"
 #include "MG_Util/Converters/MGToGL/TextureEnumConverter.h"
@@ -385,8 +386,8 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         }
         UpdateDynamicBackendParameters();
         UpdateAdvertisedExtensions();
-        if (MG_State::pGLContext) {
-            MG_State::pGLContext->InvalidateCompileEnv();
+        if (MGB_CTX_LIVE) {
+            MGB_CTX->InvalidateCompileEnv();
         }
         PopulateFormatCapabilities(physicalDevice.handle, vkGetPhysicalDeviceFormatProperties, m_vulkanCaps,
                                    MutableFormatCapabilities());
@@ -783,8 +784,8 @@ namespace MobileGL::MG_Backend::DirectVulkan {
         m_vulkanCaps = capabilities;
         UpdateDynamicBackendParameters();
         UpdateAdvertisedExtensions();
-        if (MG_State::pGLContext) {
-            MG_State::pGLContext->InvalidateCompileEnv();
+        if (MGB_CTX_LIVE) {
+            MGB_CTX->InvalidateCompileEnv();
         }
         MutableFormatCapabilities().Clear();
     }