[idd] capture: retain frames in linear buffers

Store retained frame candidates in the final linear transport layout.
Prepare texture output in local DEFAULT buffers before cadence holding.
Then publish full frames with a single buffer copy.

Keep partial damage on matching pitched layouts and leave effect-owned
buffer copies unchanged. This moves detiling out of the
deadline-critical IVSHMEM or readback transfer.

idd/LGIdd/CSwapChainProcessor.h

@@ -149,8 +149,8 @@ private:
   bool HasReadyCandidate();
   int AcquireCandidate(bool exclusiveSample);
   void ReleaseCandidate(unsigned candidateIndex);
-  bool EnsureCandidateResource(unsigned candidateIndex,
-    ID3D12Resource * source);
+  bool EnsureCandidateResource(
+    unsigned candidateIndex, size_t frameSize);
   void ResetCandidates();
   void SignalCandidateState();