Handle empty featured_image from Columbia feed

Products with no featured image return featured_image: [] (empty array) rather
than an object or null, which failed to bind to a single ColumbiaImage and
aborted the whole sync. Adds ColumbiaImageJsonConverter that reads the object
when present and yields null for any non-object form ([], false, ""), and drops
the unused GalleryImages property (we only use featured_image) to remove the
same risk. Regression tests cover both the empty-array and object cases.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/PowderCoating.Application/DTOs/Columbia/ColumbiaImageJsonConverter.cs

@@ -0,0 +1,49 @@
+using System.Text.Json;
+using System.Text.Json.Serialization;
+
+namespace PowderCoating.Application.DTOs.Columbia;
+
+/// <summary>
+/// Tolerant converter for Columbia image fields. WordPress/WooCommerce returns an object
+/// (<c>{id,src,name,alt}</c>) when an image is present, but an empty array (<c>[]</c>) — or
+/// sometimes <c>false</c>/empty string — when it is not. A single <see cref="ColumbiaImage"/>
+/// can't bind to those non-object forms, so this converter reads the object when present and
+/// yields null for anything else (consuming the token so deserialization continues).
+/// </summary>
+public class ColumbiaImageJsonConverter : JsonConverter<ColumbiaImage?>
+{
+    public override ColumbiaImage? Read(ref Utf8JsonReader reader, Type typeToConvert, JsonSerializerOptions options)
+    {
+        switch (reader.TokenType)
+        {
+            case JsonTokenType.StartObject:
+                using (var doc = JsonDocument.ParseValue(ref reader))
+                {
+                    var el = doc.RootElement;
+                    return new ColumbiaImage
+                    {
+                        Id = el.TryGetProperty("id", out var id) && id.TryGetInt32(out var i) ? i : 0,
+                        Src = GetString(el, "src"),
+                        Name = GetString(el, "name"),
+                        Alt = GetString(el, "alt"),
+                    };
+                }
+
+            case JsonTokenType.StartArray:
+                reader.Skip(); // empty/non-empty array form means "no image"
+                return null;
+
+            default:
+                // Primitive (false / "" / null / number): nothing to consume further.
+                return null;
+        }
+    }
+
+    public override void Write(Utf8JsonWriter writer, ColumbiaImage? value, JsonSerializerOptions options)
+        => throw new NotSupportedException("Columbia image fields are read-only.");
+
+    private static string GetString(JsonElement el, string property) =>
+        el.TryGetProperty(property, out var v) && v.ValueKind == JsonValueKind.String
+            ? v.GetString() ?? string.Empty
+            : string.Empty;
+}

src/PowderCoating.Application/DTOs/Columbia/ColumbiaProductDtos.cs

@@ -89,7 +89,6 @@ public class ColumbiaProduct
     public string ShortDescription { get; set; } = string.Empty;
 
     public ColumbiaImage? FeaturedImage { get; set; }
-    public List<ColumbiaImage> GalleryImages { get; set; } = new();
 
     // ── Taxonomy (arrays of {name}) — used at import to derive manufacturer/category, not stored raw ──
     public List<ColumbiaNamed> Categories { get; set; } = new();

src/PowderCoating.Infrastructure/Services/ColumbiaCoatingsApiClient.cs

@@ -32,6 +32,7 @@ public class ColumbiaCoatingsApiClient : IColumbiaCoatingsApiClient
     {
         PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
         PropertyNameCaseInsensitive = true,
+        Converters = { new ColumbiaImageJsonConverter() },
     };
 
     public ColumbiaCoatingsApiClient(

tests/PowderCoating.UnitTests/ColumbiaCatalogMapperTests.cs

@@ -230,6 +230,37 @@ public class ColumbiaCatalogMapperTests
 
     // ── End-to-end mapping invariants ─────────────────────────────────────
 
+    // ── Tolerant image deserialization (WordPress returns [] / false when empty) ──
+
+    private static readonly JsonSerializerOptions ClientJsonOptions = new()
+    {
+        PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
+        PropertyNameCaseInsensitive = true,
+        Converters = { new ColumbiaImageJsonConverter() },
+    };
+
+    [Fact]
+    public void Deserialize_FeaturedImageEmptyArray_YieldsNullImage()
+    {
+        // WordPress returns featured_image: [] for products with no image.
+        var json = """{ "sku": "X1", "name": "No Image", "featured_image": [] }""";
+        var product = JsonSerializer.Deserialize<ColumbiaProduct>(json, ClientJsonOptions);
+
+        Assert.NotNull(product);
+        Assert.Null(product!.FeaturedImage);
+        Assert.Null(ColumbiaCatalogMapper.Map(product).ImageUrl);
+    }
+
+    [Fact]
+    public void Deserialize_FeaturedImageObject_ParsesSrc()
+    {
+        var json = """{ "sku": "X1", "name": "Has Image", "featured_image": { "id": 5, "src": "https://x/img.png", "name": "i", "alt": "" } }""";
+        var product = JsonSerializer.Deserialize<ColumbiaProduct>(json, ClientJsonOptions);
+
+        Assert.Equal("https://x/img.png", product!.FeaturedImage!.Src);
+        Assert.Equal("https://x/img.png", ColumbiaCatalogMapper.Map(product).ImageUrl);
+    }
+
     [Fact]
     public void Map_AlwaysStampsSource_AndLeavesEnrichmentFieldsNull()
     {