Fix DLSS quality-change corruption and frame completion ordering

- Reprepare enc3 weights each launch to avoid stale caches after feature recreation
- Require per-slot input markers before evaluating recorded frames
- Advance split-frame timelines only through completed frames
- Add cancellation and readiness tests plus recreation consistency checks
- Update architecture and native kernel documentation

ref #8

tools/d4r_frame_completion.h

@@ -0,0 +1,34 @@
+#pragma once
+#include <cstdint>
+#include <deque>
+
+// A timeline signal releases every lower value too. Prep can cancel a later
+// frame while the CUDA worker is still producing an earlier one, so only the
+// completed prefix of admitted frames may be signalled. The caller serializes
+// admission and retirement with the same mutex used for the timeline signal.
+class D4rFrameCompletion
+{
+public:
+    void admit(uint32_t frame) { pending_.push_back({frame, false}); }
+
+    uint64_t retire(uint32_t frame)
+    {
+        for (auto& pending : pending_)
+            if (pending.frame == frame)
+            {
+                pending.done = true;
+                break;
+            }
+        while (!pending_.empty() && pending_.front().done)
+        {
+            completedThrough_ = pending_.front().frame;
+            pending_.pop_front();
+        }
+        return completedThrough_;
+    }
+
+private:
+    struct Pending { uint32_t frame; bool done; };
+    std::deque<Pending> pending_;
+    uint64_t completedThrough_ = 0;
+};