refactor: Move URLContext to internal

Moved URLContext to be an internal type within the FirebaseAI module.

This involved:
- Moving the file to `FirebaseAI/Sources/Types/Internal/Tools/URLContext.swift`.
- Removing the `public` keyword from the struct.
- Making the `Tool.urlContext()` factory method internal.
- Updating documentation comments that referenced the now-internal type.

Could not run tests due to environment limitations.

Author: google-labs-jules[bot]

FirebaseAI/Sources/Tool.swift

@@ -131,7 +131,7 @@ public struct Tool: Sendable {
     return self.init(googleSearch: googleSearch)
   }
 
-  public static func urlContext() -> Tool {
+  static func urlContext() -> Tool {
     return self.init(urlContext: URLContext())
   }
 

FirebaseAI/Sources/Types/Public/Tools/URLContext.swift renamed to FirebaseAI/Sources/Types/Internal/Tools/URLContext.swift

@@ -13,6 +13,6 @@
 // limitations under the License.
 
 @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
-public struct URLContext: Sendable, Encodable {
+struct URLContext: Sendable, Encodable {
   init() {}
 }

FirebaseAI/Sources/Types/Public/URLContextMetadata.swift

@@ -12,7 +12,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-/// Metadata related to the ``URLContext`` tool.
+/// Metadata related to the URLContext tool.
 @available(iOS 15.0, macOS 12.0, macCatalyst 15.0, tvOS 15.0, watchOS 8.0, *)
 public struct URLContextMetadata: Sendable, Hashable {
   /// List of URL context.

FirebaseAI/Sources/Types/Public/URLMetadata.swift

@@ -49,7 +49,7 @@ public struct URLMetadata: Sendable, Hashable {
       AILog.MessageCode.urlMetadataUnrecognizedURLRetrievalStatus
   }
 
-  /// The URL retrieved by the ``URLContext`` tool.
+  /// The URL retrieved by the URLContext tool.
   public let retrievedURL: URL?
 
   /// The status of the URL retrieval.