[Fix] (MG_State/MG_Impl/MG_Backend): render Flywheel instanced+indirect on both backends

Create 6 / Flywheel 1.0.6 now renders correctly with both flywheel:instancing
and flywheel:indirect on DirectGLES and DirectVulkan (verified in-game on
Adreno 830: waterwheels and cogwheels solid, animated, correct pairing, no
crashes across all four combinations).

- MG_State/MG_Impl: sync explicitly-ranged SSBO bindings of FLUSH_EXPLICIT
  persistent maps to the backend before compute dispatches. Flywheel writes
  its scatter-copy descriptors into the staging ring's persistent map and
  never flushes that span (UB per spec, works on drivers whose maps alias
  GPU-visible memory); our maps alias the CPU shadow, so the descriptors
  never reached the GPU: the scatter compute copied nothing (GLES: empty
  draw commands) or stale garbage (Vulkan: wild indirect commands ending in
  VK_ERROR_DEVICE_LOST).
- MG_Impl/MG_Backend: real glFenceSync objects backed by backend fences
  (GLES: native ES syncs guarded by context generation and owner thread;
  Vulkan: buffer-manager frame serials), replacing always-signaled stubs
  that let Flywheel reclaim staging memory the GPU still reads.
- MG_Backend/DirectGLES: compute dispatches now run the same per-program
  resource sync as draws (uniform-block bindings and sampler units must be
  re-established through the API because layout(binding) is stripped from
  transpiled ESSL) and rebind texture units afterwards; the cull shader
  used to read a stale _FlwFrameUniforms binding and the depth-pyramid
  downsample sampled a stale unit-0 texture, zeroing the Hi-Z pyramid and
  occlusion-culling all Flywheel geometry. Image uniforms are excluded from
  glUniform1i (ES bakes their unit via layout(binding)); image-unit sync is
  clamped to the device limit; eliminated/SSBO-classified uniform blocks
  are skipped.
- MG_Backend/DirectGLES: gl_BaseInstance in native indirect draws reads the
  GPU-written command buffer through an injected mg_IndirectParams SSBO
  view addressed per draw instead of the zero CPU shadow; layout(binding)
  is preserved for SSBO/image declarations (ES has no API rebinding for
  them); the ES context ownership claim moved to a global atomic owner
  thread with an EGL ground-truth check, and deferred buffer op state is
  mutex-guarded, so ops cannot silently no-op after context migration.
- MG_Backend/DirectVulkan: new RebaseInstanceIndexPass rewrites vertex
  InstanceIndex loads to (InstanceIndex - BaseInstance). glslang's relaxed
  Vulkan mode aliases gl_InstanceID to InstanceIndex, which includes
  firstInstance, but GL's gl_InstanceID is zero-based - draws with nonzero
  baseInstance paired meshes with wrong instance data (cogwheel drawn as a
  waterwheel, another wheel collapsed invisible). Gated on the
  shaderDrawParameters device feature. Sampled-read barriers additionally
  cover the compute stage (the Hi-Z downsample samples the depth
  attachment from compute), and short uniform-buffer ranges keep the
  existing zero-padding.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

MobileGL/MG_State/GLState/BufferState/BufferObject.cpp

@@ -7,6 +7,7 @@
 // End of Source File Header
 
 #include "BufferObject.h"
+#include <algorithm>
 
 namespace MobileGL::MG_State::GLState {
     namespace {
@@ -150,6 +151,21 @@ namespace MobileGL::MG_State::GLState {
         NotifySubData(m_mappedRange.start, m_mappedRange.end - m_mappedRange.start);
     }
 
+    void BufferObject::SyncMappedRangeForGpuRead(Range1D range) {
+        if (!m_isMapped) return;
+        if (!(m_mappingAccess & BufferMappingAccessBit::Persistent)) return;
+        if (!(m_mappingAccess & BufferMappingAccessBit::Write)) return;
+        // Non-FLUSH_EXPLICIT persistent maps are already covered wholesale by
+        // SyncPersistentMappedRange.
+        if (!(m_mappingAccess & BufferMappingAccessBit::FlushExplicit)) return;
+
+        const SizeT start = std::max(range.start, m_mappedRange.start);
+        const SizeT end = std::min({range.end, m_mappedRange.end, m_size});
+        if (start >= end) return;
+
+        NotifySubData(start, end - start);
+    }
+
     void BufferObject::WritebackFromBackend(DataPtr data, SizeT atOffset) {
         MOBILEGL_ASSERT(atOffset + data.size <= m_size,
                         "WritebackFromBackend out of bounds: atOffset (%zu) + data.size (%zu) > m_size (%zu)", atOffset,