[MG_Remote, MG_Pipe, MG_Impl, MG_Test, MG_IntegrationTest, Docs] (Disaggregated): inproc performance package - dirty-driven persistent-map push, batched barrier waits, spin-clock batching

VD12 Minecraft on the Redmi (FCL, DirectGLES): the split's in-world frame rate
13 -> 60-66 fps against monolith's 110-114, and persistent-map wire bytes
25 MB/frame -> ~0.23 MB/frame. The residual split-specific costs are named at
the end, not hidden: the R-1 serialization (WaitForApplied ~12%, P11's
versioned-inputs design) and a split-only mutex complex still under
investigation.

Persistent-map push, three arms picked per buffer at map time:
- mprotect dirty tracker: the mapped range's page-aligned interior is
  protected PROT_READ; the app's next write faults, the SIGSEGV handler marks
  the page in the slot's bitmap and unprotects, and the push ships one 64 KB
  block per block containing a faulted page. Ownership is three tests -
  SEGV_ACCERR only (a userspace raise and an unmapped page chain verbatim),
  inside a live tracked range, and not a refault on a still-set bit (a write
  we unprotected succeeds, so that is a non-write access and it crashes
  honestly). The alignment is INWARD: an outward-aligned edge page holds
  foreign bytes, and a signal-blocking worker thread faulting on one is a
  process kill - that was the ctest-only SmallRing segfault. Edge spans
  (at most two per map) are hashed per push and ship their containing block
  only on change (unconditional edges measured 112 MB/frame). Re-arm is one
  mprotect per contiguous run. The first push ships everything once.
- hash-suppress arm (MOBILEGL_IPC_PERSISTENT_HASH_SUPPRESS, default 1):
  per-block XXH3 against the last push's hashes; untracked buffers only.
- PushDrawConsumers: only the buffers the upcoming draw/dispatch can read
  (VAO attribs/element, indexed binding points, indirect/parameter slots,
  TexBuffer backing - the last also retires the per-frame-cadence cloud
  twitch), plus the fault-epoch skip: an unmoved epoch proves no interior
  byte changed, tracked edges are hashed in place, and any hash-arm member
  vetoes. The membership map caches the tracker slot pointer (a 64-slot
  rescan per buffer per draw was measured and removed).

MOBILEGL_IPC_BATCH_WAITS (default 1; MOBILEGL_PIPE_VERIFY forces 0): a
value-class record (kCtxState/kCtxCso/kCtxObject with no reply slot) is
published without waiting for its own apply; the barrier is taken at the next
pull-reading verb, the only place BARRIER-PULLED fields are read, so the R-1
fence posts are untouched and only the round trips between them change. Two
consequences are pinned rather than argued: kCtxObject verbs the tests read
synchronously get explicit fences (GenerateMipmapFieldsCross,
FramebufferDeathCrosses), and a frontend object whose last SharedPtr drops on
the apply thread - impossible before batching - now enqueues its
(kind, lifetimeId) on the deferred destroy queue and the GL thread replays
the DestroyAndFree helper at the verb hooks (CopyImageLayeredScenario aborted
Fatal{RoleViolation, MGPipeSlots} without it).

Doorbell::Wait's spin reads the clock once per 64 yields: on the workload
device a steady_clock read is a real syscall (no vDSO) and the per-iteration
reads were ~20% of the whole process at ~1000 waits/frame.

Gates: gen_pipe --check/--self-test green; unit 2188/2188;
integration-split 110/111, the one red being GenerateMipmapDepthPixels whose
DirectGLES and DirectVulkan MONOLITH siblings flake identically with every
code path of this package provably inert (PushIsArmed false, no ClientSession,
deferral's monolith early-out).

MobileGL/MG_Remote/Client/EmitTables.cpp

@@ -62,6 +62,7 @@
 #include <MG_Impl/Pipe/FramebufferEmit.h>
 #include <MG_Impl/Pipe/PipeFill.h>
 #include <MG_Impl/Pipe/TextureEmit.h>
+#include <MG_Pipe/PipeMutation.h>
 
 namespace MobileGL::MG_Remote::Client {
 
@@ -214,16 +215,23 @@ namespace MobileGL::MG_Remote::Client {
 
         // The two hooks b1 wrote and deliberately left with no caller, because the call site is
         // this file's. ORDER: the push first (it produces resource_subdata records that must
-        // precede the verb on SEG_CMD), then the mark walk, then the verb record.
+        // precede the verb on SEG_CMD), then the mark walk, then the verb record. The deferred
+        // destroy drain rides the same boundary: it replays, on this GL thread, the death
+        // announcements whose last SharedPtr dropped on the apply thread (PipeMutation.h's
+        // deferred destroy queue), and its records must also precede this verb.
         void BeforeDrawVerb() {
-            PushPersistentMapsBeforeVerb();
+            PersistentMapTracker::Instance().PushDrawConsumers();
+            MG_Pipe::MGPipeDrainDeferredDestroys();
             MarkGpuWritesForDraw();
         }
 
         // A verb that reads buffers but starts no shader: clear, blit, readback, present. The
         // push still has to run - a coherent map is read by the GPU on any of them - but there
         // is no shader that could write one, so no mark walk.
-        void BeforeReadOnlyVerb() { PushPersistentMapsBeforeVerb(); }
+        void BeforeReadOnlyVerb() {
+            PushPersistentMapsBeforeVerb();
+            MG_Pipe::MGPipeDrainDeferredDestroys();
+        }
 
         // =============================================================================
         // CLASS B - the five slots the verb census measured (CONTRACT-P5.md §7)
@@ -1110,7 +1118,7 @@ namespace MobileGL::MG_Remote::Client {
         // slot would inherit a call site that was already correct.
         void EmitDispatchCompute(GLuint numGroupsX, GLuint numGroupsY, GLuint numGroupsZ) {
             ClientSession& session = RequireSession("DispatchCompute");
-            PushPersistentMapsBeforeVerb();
+            PersistentMapTracker::Instance().PushDrawConsumers();
             MarkGpuWritesForDispatch();
 
             MG_Pipe::MGPGridInfo record{};
@@ -1129,7 +1137,7 @@ namespace MobileGL::MG_Remote::Client {
 
         void EmitDispatchComputeIndirect(GLintptr indirect) {
             ClientSession& session = RequireSession("DispatchComputeIndirect");
-            PushPersistentMapsBeforeVerb();
+            PersistentMapTracker::Instance().PushDrawConsumers();
             MarkGpuWritesForDispatch();
 
             MG_Pipe::MGPGridInfo record{};