Check image counts against the limits vendors state

app/MindWork AI Studio/Assistants/VisualBriefing/VisualBriefingBuildOrchestrator.Inputs.cs

@@ -277,6 +277,21 @@ internal sealed partial class VisualBriefingBuildOrchestrator
                 VisualBriefingBuildStage.SOURCE_PREPARATION,
                 "The selected model cannot process the number of source images and visual assets.",
                 $"ImageCount={imageSources.Length}; SingleImage={profile.Has(Capability.SINGLE_IMAGE_INPUT)}; MultipleImages={profile.Has(Capability.MULTIPLE_IMAGE_INPUT)}.");
+
+        //
+        // And then the number, where a vendor has stated one. Without it, "takes several images"
+        // is all the check above can ask, and a briefing of two hundred pictures passes it only to
+        // be refused by the provider after everything has been read, uploaded and paid for.
+        //
+        // No limit is invented where none is documented. A model whose vendor says nothing keeps
+        // the answer it has always had, which is that several means several.
+        //
+        if (profile.Images.MaxInOneMessage is { } allowed && imageSources.Length > allowed)
+            throw new VisualBriefingBuildException(
+                VisualBriefingFailureCode.MODEL_CAPABILITY_MISSING,
+                VisualBriefingBuildStage.SOURCE_PREPARATION,
+                $"The selected model accepts at most {allowed} images at once, and this briefing uses {imageSources.Length}.",
+                $"ImageCount={imageSources.Length}; MaxPerMessage={profile.Images.MaxPerMessage}; MaxPerRequest={profile.Images.MaxPerRequest}.");
     }
 
     /// <summary>