[iOS] [AIChat] Support tools for custom models (#34944)

This adds a new toggle to the custom model form to allow the user to control whether or not the local modal supports tools

ios/brave-ios/Sources/AIChat/AIChatStrings.swift

@@ -1203,6 +1203,20 @@ extension Strings {
       value: "If this model takes image as input, e.g. llama 3.2b vision",
       comment: "The description text explaining what vision support means with an example"
     )
+    public static let customModelFormSupportsToolsFieldTitle = NSLocalizedString(
+      "aichat.customModelFormToolsSupportFieldTitle",
+      tableName: "BraveLeo",
+      bundle: .module,
+      value: "Tools support",
+      comment: "The label for the tools support toggle"
+    )
+    public static let customModelFormSupportsToolsFieldDescription = NSLocalizedString(
+      "aichat.customModelFormToolsSupportFieldDescription",
+      tableName: "BraveLeo",
+      bundle: .module,
+      value: "If this model supports function calling/tool use",
+      comment: "The description text explaining what tools supports means"
+    )
     public static let customModelFormSystemPromptFieldTitle = NSLocalizedString(
       "aichat.customModelFormSystemPromptFieldTitle",
       tableName: "BraveLeo",

ios/brave-ios/Sources/AIChat/WebUI/AIChatCustomModelForm.swift

@@ -30,6 +30,7 @@ struct CustomModelForm: View {
     var apiKey: String?
     var systemPrompt: String?
     var visionSupport: Bool = false
+    var supportsTools: Bool = false
 
     var isRequiredDataFilled: Bool {
       return !displayName.isEmpty && !requestName.isEmpty && !serverEndpoint.isEmpty
@@ -200,6 +201,12 @@ struct CustomModelForm: View {
         }
         .tint(Color(braveSystemName: .primary40))
         .listRowBackground(Color(.secondaryBraveGroupedBackground))
+        Toggle(isOn: $data.supportsTools) {
+          Text(Strings.AIChat.customModelFormSupportsToolsFieldTitle)
+          Text(Strings.AIChat.customModelFormSupportsToolsFieldDescription)
+        }
+        .tint(Color(braveSystemName: .primary40))
+        .listRowBackground(Color(.secondaryBraveGroupedBackground))
       }
 
       Section {
@@ -253,6 +260,7 @@ struct CustomModelForm: View {
       if let initialModel {
         data.displayName = initialModel.displayName
         data.visionSupport = initialModel.visionSupport
+        data.supportsTools = initialModel.supportsTools
         if let customOptions = initialModel.options.customModelOptions {
           data.requestName = customOptions.modelRequestName
           data.serverEndpoint = customOptions.endpoint.absoluteString
@@ -311,6 +319,7 @@ struct CustomModelForm: View {
     }
     let model = AiChat.Model()
     model.visionSupport = data.visionSupport
+    model.supportsTools = data.supportsTools
     model.displayName = data.displayName
     model.options = .init(
       customModelOptions: .init(