fix(505): gate the OpenCL tonemap on the ACTUAL frame location, not an enumeration

UseOpenClTonemap excluded the two known ways frames reach a hardware surface
before the tonemap (the QSV decoder, deinterlace_qsv). That is only correct for
as long as the enumeration stays complete -- and the failure mode if it ever
stops being complete is a second hwupload stacked on frames that are already on
a surface.

Check currentState.FrameDataLocation directly instead. The route begins with
hwupload, so "frames are in software" is the actual precondition; the specific
exclusions stay as documentation of the known cases, but the state check is what
makes it safe. A future filter landing ahead of the tonemap now degrades to the
software tonemap rather than emitting a broken graph.

ErsatzTV.FFmpeg/Pipeline/QsvPipelineBuilder.cs

@@ -222,7 +222,7 @@ public class QsvPipelineBuilder : SoftwarePipelineBuilder
         // the plan the downscale has to happen in scale_vaapi rather than vpp_qsv, because a QSV
         // surface can be mapped neither to OpenCL nor back to VA-API. Decided once, up front, so
         // the scale and tonemap steps cannot disagree about which device the frames are on.
-        bool useOpenClTonemap = UseOpenClTonemap(videoStream, context, ffmpegState);
+        bool useOpenClTonemap = UseOpenClTonemap(videoStream, context, ffmpegState, currentState);
 
         // _logger.LogDebug("After decode: {PixelFormat}", currentState.PixelFormat);
         currentState = SetDeinterlace(videoInputFile, context, ffmpegState, currentState);
@@ -671,13 +671,27 @@ public class QsvPipelineBuilder : SoftwarePipelineBuilder
     // The QSV pipeline can only reach tonemap_opencl through the VA-API device that its own QSV
     // device is derived from, so every condition here is about that device existing and being
     // reachable with software frames in hand.
-    private bool UseOpenClTonemap(VideoStream videoStream, PipelineContext context, FFmpegState ffmpegState)
+    private bool UseOpenClTonemap(
+        VideoStream videoStream,
+        PipelineContext context,
+        FFmpegState ffmpegState,
+        FrameState currentState)
     {
         if (!videoStream.ColorParams.IsHdr)
         {
             return false;
         }
 
+        // The backstop for every case below, and for any future filter that lands ahead of the
+        // tonemap: the route starts with hwupload, so the frames have to actually be in software.
+        // Checked against the state rather than inferred from the enumeration, so a later change
+        // that puts frames on a surface earlier degrades to the software tonemap instead of
+        // emitting a second upload on top of an existing one.
+        if (currentState.FrameDataLocation == FrameDataLocation.Hardware)
+        {
+            return false;
+        }
+
         // ffmpeg has no vaapi on Windows, so there is no device to derive OpenCL from
         if (OperatingSystem.IsWindows())
         {