refactor(forms): expose consequentialHint annotation

Unlike `readOnlyHint` and `untrustedContentHint`, Angular cannot infer any reasonable default value for `consequentialHint` and simply exposes it to users to specify as appropriate.

See: https://groups.google.com/a/chromium.org/g/chrome-ai-dev-preview/c/uHu5kfclbKw/m/dgorjfHPDgAJ

goldens/public-api/forms/signals/index.api.md

@@ -213,6 +213,9 @@ export interface FormOptions<TModel> {
     experimentalWebMcpTool?: {
         name: string;
         description: string;
+        annotations?: {
+            consequentialHint?: boolean;
+        };
     };
     injector?: Injector;
     name?: string;

packages/forms/signals/src/api/structure.ts

@@ -69,6 +69,20 @@ export interface FormOptions<TModel> {
 
     /** A description of the tool's purpose and usage information. */
     description: string;
+
+    /**
+     * Set of configuration values extending the core tool behavior.
+     */
+    annotations?: {
+      // `readOnlyHint` and `untrustedContentHint` are intentionally omitted as they have
+      // hard-coded values.
+
+      /**
+       * A hint that the tool will have consequential effects like mutating state or interacting
+       * with the external world.
+       */
+      consequentialHint?: boolean;
+    };
   };
 
   /** Options that define how to handle form submission. */
@@ -232,6 +246,7 @@ export function form<TModel>(...args: any[]): FieldTree<TModel> {
         registerWebMcpForm(fieldRoot.fieldTree, {
           name: experimentalWebMcpTool.name,
           description: experimentalWebMcpTool.description,
+          annotations: experimentalWebMcpTool.annotations,
         }),
       );
     } else {

packages/forms/signals/src/webmcp/registration.ts

@@ -37,7 +37,7 @@ const registerWebMcpForm: RegisterWebMcpForm = (formTree, options) => {
 
 async function initWebMcpForm(
   formTree: FieldTree<unknown>,
-  options: {name: string; description: string},
+  options: {name: string; description: string; annotations?: {consequentialHint?: boolean}},
   injector: Injector,
 ) {
   const node = formTree() as FieldNode;
@@ -56,6 +56,8 @@ async function initWebMcpForm(
       description: options.description,
       inputSchema,
       annotations: {
+        ...options.annotations,
+
         // Forms are assumed to implicitly mutate the DOM (otherwise how would a user interact with them?)
         // and therefore are _never_ read-only.
         readOnlyHint: false,

packages/forms/signals/src/webmcp/tokens.ts

@@ -22,5 +22,5 @@ export const REGISTER_WEBMCP_FORM = new InjectionToken<RegisterWebMcpForm>(
  */
 export type RegisterWebMcpForm = (
   form: FieldTree<unknown>,
-  options: {name: string; description: string},
+  options: {name: string; description: string; annotations?: {consequentialHint?: boolean}},
 ) => Promise<void>;