Add test for API Collection icon rendering in external references

Adds test to verify that API Collections (articles with Topics sections) are correctly identified as .collectionGroup kind in linkable entities, ensuring cross-framework references display the correct icon. The test is temporarily skipped until the fix is implemented in the next commit.

rdar://135837611

Author: RalucaP

Tests/SwiftDocCTests/LinkTargets/LinkDestinationSummaryTests.swift

@@ -829,4 +829,53 @@ class LinkDestinationSummaryTests: XCTestCase {
             "doc://com.example.mymodule/documentation/MyModule/MyClass/myFunc()-9a7po",
         ])
     }
+
+    /// Tests that API Collections (articles with Topics sections) are correctly identified as `.collectionGroup`
+    /// kind in linkable entities, ensuring cross-framework references display the correct icon.
+    func testAPICollectionKindForLinkDestinationSummary() async throws {
+        throw XCTSkip("Test will be enabled after implementing the fix")
+
+        let symbolGraph = makeSymbolGraph(
+            moduleName: "TestModule",
+            symbols: [makeSymbol(id: "test-class", kind: .class, pathComponents: ["TestClass"])]
+        )
+
+        let catalogHierarchy = Folder(name: "unit-test.docc", content: [
+            TextFile(name: "APICollection.md", utf8Content: """
+                # Time Pitch Algorithm Settings
+
+                This is an API Collection that curates symbols.
+
+                ## Topics
+
+                ### Algorithms
+                - ``TestModule/TestClass``
+                """),
+            JSONFile(name: "TestModule.symbols.json", content: symbolGraph),
+            InfoPlist(displayName: "TestBundle", identifier: "com.test.example")
+        ])
+
+        let (_, context) = try await loadBundle(catalog: catalogHierarchy)
+        let converter = DocumentationNodeConverter(context: context)
+
+        let apiCollectionReference = ResolvedTopicReference(
+            bundleID: context.inputs.id,
+            path: "/documentation/TestBundle/APICollection",
+            sourceLanguage: .swift
+        )
+        let node = try context.entity(with: apiCollectionReference)
+        let renderNode = converter.convert(node)
+
+        let summaries = node.externallyLinkableElementSummaries(context: context, renderNode: renderNode)
+        let pageSummary = summaries[0]
+
+        XCTAssertEqual(pageSummary.kind, .collectionGroup)
+        XCTAssertEqual(pageSummary.title, "Time Pitch Algorithm Settings")
+        XCTAssertEqual(pageSummary.abstract, [.text("This is an API Collection that curates symbols.")])
+
+        // Verify round-trip encoding preserves the correct kind
+        let encoded = try JSONEncoder().encode(pageSummary)
+        let decoded = try JSONDecoder().decode(LinkDestinationSummary.self, from: encoded)
+        XCTAssertEqual(decoded.kind, .collectionGroup)
+    }
 }