Add realm config templates

packages/base/card-api.gts

@@ -1567,6 +1567,7 @@ class LinksTo<CardT extends LinkableDefConstructor> implements Field<CardT> {
           format?: Format;
           displayContainer?: boolean;
           typeConstraint?: ResolvedCodeRef;
+          lockConsumingRealm?: boolean;
         };
       };
       Blocks: {};
@@ -1583,6 +1584,7 @@ class LinksTo<CardT extends LinkableDefConstructor> implements Field<CardT> {
                   @field={{linksToField}}
                   @brokenLink={{broken}}
                   @typeConstraint={{@typeConstraint}}
+                  @lockConsumingRealm={{@lockConsumingRealm}}
                   @createCard={{cardCrudFunctions.createCard}}
                   ...attributes
                 />

packages/base/field-component.gts

@@ -49,6 +49,13 @@ export interface BoxComponentSignature {
       format?: Format;
       displayContainer?: boolean;
       typeConstraint?: ResolvedCodeRef;
+      /**
+       * When true (only meaningful on linksTo / linksToMany editors),
+       * hard-scope the card chooser to the consuming realm — the realm
+       * picker in the catalog modal is locked and the user cannot pick
+       * a card from another realm. UI hint only; no runtime validation.
+       */
+      lockConsumingRealm?: boolean;
     };
   };
   Blocks: {};

packages/base/links-to-editor.gts

@@ -51,6 +51,12 @@ interface Signature {
     field: Field<LinkableDefConstructor>;
     brokenLink?: BrokenLink;
     typeConstraint?: ResolvedCodeRef;
+    /**
+     * When true, hard-scope the card chooser to the consuming realm
+     * (the realm of the parent card). The catalog modal's realm picker
+     * is locked. UI hint only; no runtime validation.
+     */
+    lockConsumingRealm?: boolean;
     createCard?: CreateCardFn;
   };
 }
@@ -235,6 +241,7 @@ export class LinksToEditor extends GlimmerComponent<Signature> {
         },
         createNewCard: this.args.createCard,
         consumingRealm: this.realmURL,
+        lockConsumingRealm: this.args.lockConsumingRealm,
       },
     );
     if (cardId) {