Add test for API Collection icon rendering in external references

Adds tests 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. Includes regression test for explicit @pagekind(article) metadata override behavior to ensure the fix doesn't break existing functionality. The first test is temporarily skipped until the fix is implemented in the next commit.

rdar://135837611

Author: RalucaP

Tests/SwiftDocCTests/LinkTargets/LinkDestinationSummaryTests.swift

@@ -829,4 +829,96 @@ 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: """
+                # API Collection
+
+                This is an API Collection that curates symbols.
+
+                ## Topics
+
+                - ``TestModule/TestClass``
+                """),
+            JSONFile(name: "TestModule.symbols.json", content: symbolGraph)
+        ])
+
+        let (_, context) = try await loadBundle(catalog: catalogHierarchy)
+        let converter = DocumentationNodeConverter(context: context)
+
+        let apiCollectionReference = ResolvedTopicReference(
+            bundleID: context.inputs.id,
+            path: "/documentation/unit-test/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 = try XCTUnwrap(summaries.first)
+
+        XCTAssertEqual(pageSummary.kind, .collectionGroup)
+        XCTAssertEqual(pageSummary.title, "API Collection")
+        XCTAssertEqual(pageSummary.abstract, [.text("This is an API Collection that curates symbols.")])
+
+        // Verify round-trip encoding preserves the correct kind
+        try assertRoundTripCoding(pageSummary)
+    }
+
+    /// Tests that explicit `@PageKind(article)` metadata overrides API Collection detection,
+    /// ensuring that explicit page kind directives take precedence over automatic detection.
+    func testExplicitPageKindOverridesAPICollectionDetection() async throws {
+        let symbolGraph = makeSymbolGraph(
+            moduleName: "TestModule",
+            symbols: [makeSymbol(id: "test-class", kind: .class, pathComponents: ["TestClass"])]
+        )
+
+        let catalogHierarchy = Folder(name: "unit-test.docc", content: [
+            TextFile(name: "ExplicitArticle.md", utf8Content: """
+                # Explicit Article
+
+                This looks like an API Collection but is explicitly marked as an article.
+
+                @Metadata {
+                    @PageKind(article)
+                }
+
+                ## Topics
+
+                - ``TestModule/TestClass``
+                """),
+            JSONFile(name: "TestModule.symbols.json", content: symbolGraph)
+        ])
+
+        let (_, context) = try await loadBundle(catalog: catalogHierarchy)
+        let converter = DocumentationNodeConverter(context: context)
+
+        let explicitArticleReference = ResolvedTopicReference(
+            bundleID: context.inputs.id,
+            path: "/documentation/unit-test/ExplicitArticle",
+            sourceLanguage: .swift
+        )
+        let node = try context.entity(with: explicitArticleReference)
+        let renderNode = converter.convert(node)
+
+        let summaries = node.externallyLinkableElementSummaries(context: context, renderNode: renderNode)
+        let pageSummary = try XCTUnwrap(summaries.first)
+
+        // Should be .article because of explicit @PageKind(article), not .collectionGroup
+        XCTAssertEqual(pageSummary.kind, .article)
+        XCTAssertEqual(pageSummary.title, "Explicit Article")
+
+        // Verify round-trip encoding preserves the correct kind
+        try assertRoundTripCoding(pageSummary)
+    }
 }