Refine Columbia sync after first live run

Fixes from reviewing the first full sync of the real catalog:

- Exclude non-powder / size-variant listings: physical swatch cards (-SW /
  "SWATCH"), 4 oz testers (-04 / "Tester"), and 5 lb sample bags ("Sample (").
  These are not standalone powder colors. Filtered before mapping, and a
  cleanup step deletes any already synced (so they're removed, not flagged
  discontinued). Sample detection keys off the "Sample (" name, not the bare
  -S suffix, to avoid catching a real SKU ending in S (verified 0 collisions).
- Tighten RequiresClearCoat: was flagging ~53% of the catalog on any casual
  "clear coat" mention. Now only genuine signals (partial-cure schedules, the
  Illusion line, explicit "requires a clear" phrasing) trip it.
- Fix literal "—" in the sync success banner (TempData is HTML-encoded).

Tests cover the exclusion patterns and the tightened clear-coat detection.

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

src/PowderCoating.Infrastructure/Services/Columbia/ColumbiaCatalogSyncService.cs

@@ -57,7 +57,9 @@ public class ColumbiaCatalogSyncService : IColumbiaCatalogSyncService
             result.TotalFetched = products.Count;
 
             // Map and de-duplicate by (VendorName, SKU) in case the feed repeats a SKU.
+            // Exclude swatch cards and tester/sample size-variants — not standalone powder colors.
             var mapped = products
+                .Where(p => !ColumbiaCatalogMapper.IsExcludedProduct(p))
                 .Select(ColumbiaCatalogMapper.Map)
                 .Where(m => !string.IsNullOrWhiteSpace(m.Sku))
                 .GroupBy(m => $"{m.VendorName}|{m.Sku}", StringComparer.OrdinalIgnoreCase)
@@ -70,6 +72,10 @@ public class ColumbiaCatalogSyncService : IColumbiaCatalogSyncService
             result.Unchanged = upsertResult.Unchanged;
             result.Skipped = upsertResult.Skipped;
 
+            // Remove any excluded records (swatches) that were synced before the exclusion existed,
+            // so they're deleted outright rather than lingering as "discontinued" powders.
+            await RemoveExcludedRecordsAsync();
+
             // Complete pull succeeded — safe to reconcile discontinuations.
             var incomingKeys = mapped
                 .Select(m => $"{m.VendorName}|{m.Sku}")
@@ -136,6 +142,32 @@ public class ColumbiaCatalogSyncService : IColumbiaCatalogSyncService
         return (discontinued, reactivated);
     }
 
+    /// <summary>
+    /// Deletes Columbia-sourced catalog rows that should not be in the catalog (swatch cards and
+    /// tester/sample size-variants). Mirrors <see cref="ColumbiaCatalogMapper.IsExcludedProduct"/>
+    /// on the stored columns. A no-op once the catalog is clean; guards against records synced
+    /// before the exclusion rule and ensures excluded items are removed, not flagged discontinued.
+    /// </summary>
+    private async Task RemoveExcludedRecordsAsync()
+    {
+        var excluded = (await _unitOfWork.PowderCatalog.FindAsync(p =>
+            p.Source == ColumbiaIntegrationConstants.SourceName
+            && (p.Sku.EndsWith("-SW")
+                || p.Sku.EndsWith("-04")
+                || p.ColorName.Contains("SWATCH")
+                || p.ColorName.Contains("Tester")
+                || p.ColorName.Contains("Sample (")))).ToList();
+
+        if (excluded.Count == 0)
+            return;
+
+        foreach (var e in excluded)
+            await _unitOfWork.PowderCatalog.DeleteAsync(e);
+        await _unitOfWork.CompleteAsync();
+
+        _logger.LogInformation("Columbia sync: removed {Count} excluded record(s) (swatch/tester/sample) from the catalog.", excluded.Count);
+    }
+
     /// <summary>Persists the run outcome to the last-synced / last-result platform settings.</summary>
     private async Task RecordResultAsync(ColumbiaSyncResult result)
     {