[MG_Backend] (Disaggregated): P5e ID-124 - the pull and push flavours compile again

Three sites, all pre-existing at 7c6f6886, all the same disease: something guarded by
MOBILEGL_BUILD_DISAGGREGATED used from code that is not. Nothing in the gate built either
flavour, so nobody knew.

- Managers.cpp: StagedTextureTargetForPipeTarget is a pure MGPipeResourceTarget -> TextureTarget
  switch with no wire, no record and no role in it, but it sat inside a nested
  #if MOBILEGL_BUILD_DISAGGREGATED while its only caller MGB_TEXPARAM_TARGET is guarded by
  #if MOBILEGL_PIPE_PUSH alone. Let out of the inner block without moving any text. The narrower
  fix - guarding the macro block too - is WRONG and was tried: that block also carries
  TextureDiagName and MGB_TEXTURE_RECORD_ARM_SELECTED, which the push flavour does need, and
  removing them broke it differently.
- DirectGLES.cpp:5575: the storage-block-signature clause called
  ComputeShaderStorageBlockBindingSignatureOf, declared only under MOBILEGL_PIPE_PUSH, from an
  UNGUARDED condition list. The clause is push-only in substance too - the signature it compares
  is over the override map the wire carries.
- DirectGLES.cpp BindCurrentTextures: keysMatch was declared inside
  #if MOBILEGL_BUILD_DISAGGREGATED while the ternary's else-arm and every use sat outside it.
  The legacy arm becomes a LAZY lambda, not an eager Bool: it reads currentProgram, which is
  null on the handle arm after pa, so the laziness the ternary gave for free is load-bearing
  (ID-81 / ID-110 - the arm decides, and the other arm's reads must not happen at all).

Gate: flavours rc=0 - pull 915 TUs (push define absent), push 929 TUs (push=1), both arms
asserted against compile_commands.json rather than against the flags, because the first version
of this step passed -DMOBILEGL_PIPE_PUSH=OFF beside an option that implies it and reported a
clean 982-TU "pull" build that was a second copy of the split build. The cache entry still read
OFF. Split build unaffected.

MobileGL/MG_Backend/DirectGLES/DirectGLES.cpp

@@ -5724,8 +5724,15 @@ namespace MobileGL::MG_Backend::DirectGLES {
                 twin->GetSnormFallbackClampOutputMask() != g_snormFallbackClampOutputMask ||
                 twin->GetUnormFallbackClampOutputMask() != g_unormFallbackClampOutputMask ||
                 twin->GetFragColorBroadcastCount() != g_fragColorBroadcastCount ||
+#if MOBILEGL_PIPE_PUSH
+                // P5e (ID-124): ComputeShaderStorageBlockBindingSignatureOf is declared only
+                // under MOBILEGL_PIPE_PUSH (Managers.h:3122) and this clause read it from an
+                // UNGUARDED condition list, so the pull flavour did not compile. The clause is
+                // push-only in substance too: the signature it compares is over the override
+                // map the wire carries, and without the wire there is nothing to compare.
                 twin->GetShaderStorageBlockBindingSignature() !=
                     ComputeShaderStorageBlockBindingSignatureOf(*currentProgram) ||
+#endif
                 // A fourth of the same shape, and the reason glBindImageTexture itself does
                 // nothing: GLSL ES demands a format layout qualifier on an image where desktop
                 // GLSL lets a writeonly declaration omit one, so a format-less declaration is
@@ -6936,16 +6943,15 @@ namespace MobileGL::MG_Backend::DirectGLES {
         const SizeT shadowBytes =
             static_cast<SizeT>(maxTouchedUnit + 1) * sizeof(TextureImpl::g_boundTexturesCache[0]);
         const Uint64 unitBindingsEpoch = keys.unitBindingsEpoch;
-#if MOBILEGL_BUILD_DISAGGREGATED
-        const Bool keysMatch =
-            byHandle ? (memo.valid && memo.byHandle && memo.maxTouchedUnit == maxTouchedUnit &&
-                        memo.contextSerial == contextSerial && memo.samplerViewsSerial == samplerViewsSerial &&
-                        memo.drawProgram.Slot == drawProgram.Slot && memo.drawProgram.Gen == drawProgram.Gen &&
-                        memo.shaderCsoSerial == shaderCsoSerial && memo.bindingsSerial == bindingsSerial &&
-                        memo.contextGeneration == g_backendContextGeneration)
-                     :
-#endif
-                     (memo.valid && memo.glContextId == keys.contextId &&
+        // P5e (ID-124): the legacy key is a LAZY LAMBDA, not an eagerly-computed Bool. It was
+        // the else-arm of a ternary whose declaration sat inside `#if MOBILEGL_BUILD_DISAGGREGATED`
+        // while the arm itself and every use of `keysMatch` sat outside it, so neither
+        // non-disaggregated flavour compiled. Hoisting it to an eager Bool would have been
+        // WORSE than the build break: it reads `currentProgram`, which is null on the handle
+        // arm, so the laziness the ternary gave for free is load-bearing (ID-81 / ID-110 -
+        // the arm decides, and the other arm's reads must not happen at all).
+        const auto legacyKeysMatch = [&]() -> Bool {
+            return (memo.valid && memo.glContextId == keys.contextId &&
                                memo.maxTouchedUnit == maxTouchedUnit &&
                                memo.unitBindingsEpoch == unitBindingsEpoch &&
                                memo.samplingResolutionGeneration == keys.samplingGeneration &&
@@ -6955,6 +6961,18 @@ namespace MobileGL::MG_Backend::DirectGLES {
                                    (currentProgram ? currentProgram->GetBackendStateVersion() : 0) &&
                                memo.programLinked == (currentProgram && currentProgram->GetLinkStatus()) &&
                                memo.contextGeneration == g_backendContextGeneration);
+        };
+#if MOBILEGL_BUILD_DISAGGREGATED
+        const Bool keysMatch =
+            byHandle ? (memo.valid && memo.byHandle && memo.maxTouchedUnit == maxTouchedUnit &&
+                        memo.contextSerial == contextSerial && memo.samplerViewsSerial == samplerViewsSerial &&
+                        memo.drawProgram.Slot == drawProgram.Slot && memo.drawProgram.Gen == drawProgram.Gen &&
+                        memo.shaderCsoSerial == shaderCsoSerial && memo.bindingsSerial == bindingsSerial &&
+                        memo.contextGeneration == g_backendContextGeneration)
+                     : legacyKeysMatch();
+#else
+        const Bool keysMatch = legacyKeysMatch();
+#endif
         // Short-circuited: the shadow compare is only meaningful once the key (and with it the
         // snapshotted row count) matches.
         if (!keysMatch || std::memcmp(memo.boundTextures.data(), TextureImpl::g_boundTexturesCache.data(),

MobileGL/MG_Backend/DirectGLES/Managers.cpp

@@ -2671,6 +2671,14 @@ namespace MobileGL::MG_Backend::DirectGLES {
                 }
             }
 
+// P5e (ID-124): OUT OF THE DISAGGREGATED BLOCK ON PURPOSE. This is a pure
+// MGPipeResourceTarget -> TextureTarget switch with no wire, no record and no role in it, but
+// it sat inside the nested `#if MOBILEGL_BUILD_DISAGGREGATED` below while its only caller,
+// MGB_TEXPARAM_TARGET, is guarded by `#if MOBILEGL_PIPE_PUSH` alone - so a push build without
+// disaggregation did not compile. The narrower fix (guarding the macro block too) is wrong:
+// that block also carries TextureDiagName and MGB_TEXTURE_RECORD_ARM_SELECTED, which the push
+// flavour does need. Caught by the `flavours` gate step; see ID-124.
+#endif // MOBILEGL_BUILD_DISAGGREGATED
             // The inverse of MG_Pipe::MGPipeResourceTargetForTextureTarget, for the sync's
             // target reads (ConvertTextureTargetToBackendGLEnum and MapToBackendTextureTarget
             // both want the frontend enum).
@@ -2690,6 +2698,7 @@ namespace MobileGL::MG_Backend::DirectGLES {
                 default: return TextureTarget::Unknown;
                 }
             }
+#if MOBILEGL_BUILD_DISAGGREGATED
 
             void Ops_H_TextureSubData(MG_Pipe::MGPipeHandle res, const MG_Pipe::MGPSubData& record,
                                       const void* bytes, const MG_Pipe::MGPSubRegion* regions) {