[Config, MG_Backend, MG_Test] (Disaggregated): P5e c0e - the two knobs and the caps arm

- IpcTable::RunAhead (MOBILEGL_IPC_RUN_AHEAD, default 1, forced 0 under PipeVerify beside
  BatchWaits) and IpcTable::PresentCredit (MOBILEGL_IPC_PRESENT_CREDIT, default 1, range
  1..8). Both parsed unconditionally like every other IPC knob and both in the IPC log
  line, because a knob that silently means nothing on one arm of an A/B is how an A/B
  stops being one.
- RUN_AHEAD=0 is an A/B CONTROL and not a negative one: identical server code, identical
  records, identical fill decision, and only the client's wait differs. VERB_BARRIER=0
  keeps its own meaning as the lockstep arm's negative control.
- MG_Backend/Init.cpp: kMGPipeP5eRunAheadReady = false, and the caps arm goes through
  MGPipeRunAheadCapBitsFor so the "DirectGLES only, and only once the integration commit
  flips the constant" decision has one spelling. A constant and not a knob: an operator
  must not be able to turn a half-migrated server into a run-ahead one, because the
  failure mode is a torn read that renders wrong rather than aborting.
- MagmaPipeIdentityTest pins both halves - no bit 10 for DirectVulkan whatever the
  integration constant says, bit 10 for DirectGLES only when it is true, and that one bit
  and nothing else.
- The push default becomes kMGPipeSubsystemsMigratedAtP5e (0x3fff). Inert: bit 13 is not
  in kMGPipeWiredSubsystems, so no emission gate opens on it; 0x1fff survives as P5e's
  "everything P4a had and nothing of mine" control.

MobileGL/MG_Backend/Init.cpp

@@ -81,6 +81,22 @@ namespace MobileGL::MG_Backend {
         // DirectVulkan registers NO resource ops - MGPipeSetResourceOps has exactly one caller
         // in the whole tree and it is Managers.cpp:2594 - so bit 7 is CLEAR for it, which is
         // the same fact ObjectSubsystemControlScenario already pins from the client side.
+        // P5e (MG_Remote/CONTRACT-P5E.md §6.2). THE ONE CONSTANT THE WHOLE PHASE HANGS ON.
+        //
+        // kCapRunAheadApply says "this server applies an unbarriered record without reading
+        // client memory". That is only true once EVERY per-draw family reads records instead
+        // of the frontend - vi, sb, pg, tx2 and fb all land before it is - so the caps arm
+        // below is gated on this constant, which the P5e INTEGRATION COMMIT flips to true
+        // after the last of them. Until then every P5e package lands with the wait rule, the
+        // static WaitClass column and the barriered predicate compiled and INERT: the client
+        // never latches RunAheadArmed, so it runs today's lockstep path byte for byte.
+        //
+        // It is a constant and not a knob on purpose. An operator cannot turn a half-migrated
+        // server into a run-ahead one, because the failure mode is not a slow frame - it is
+        // the apply thread reading client memory that has already moved, which renders wrong
+        // rather than aborting.
+        constexpr Bool kMGPipeP5eRunAheadReady = false;
+
         Uint64 ConsumedSubsystemsFor(BackendType type) {
             switch (type) {
             case BackendType::DirectGLES: return MG_Pipe::kMGPipeSubsystemsMigratedAtP4a;
@@ -166,6 +182,21 @@ namespace MobileGL::MG_Backend {
                 serverBackend->GetBackendFunctions().GL.EndTransformFeedback != nullptr) {
                 capBits |= MG_Pipe::kCapBackendOwnsXfbCapture;
             }
+            // P5e (CONTRACT-P5E.md §1, §6): kCapRunAheadApply, THE DIRECTGLES ARM AND ONLY IT.
+            //
+            // Magma is deliberately absent and is not an omission: it keeps the lockstep for
+            // the whole of P5e, its four apply-thread allocator sites are real debt P7 retires,
+            // and MGPipeApplierCurrentRecordIsBarriered() answers true for every record on a
+            // server that does not publish this bit - which is exactly what keeps those probes
+            // and its BARRIER_PULLED reads inside P5C's semantics and its rsp accounting
+            // honest. Publishing the bit here for DirectVulkan would turn accounted pulls into
+            // torn ones, so MagmaPipeIdentityTest pins its absence.
+            //
+            // The Espryt arm is gated on kMGPipeP5eRunAheadReady, which is false until the
+            // integration commit: the bit is what ARMS the client, so every package before it
+            // lands inert.
+            capBits |= MG_Pipe::MGPipeRunAheadCapBitsFor(MG_Config::ActiveBackendType,
+                                                         kMGPipeP5eRunAheadReady);
             session.SetCapabilityBits(capBits);
             session.SetBackend(loop.Backend());