feat: add removable reference feature vertical slice

src/application/create-application.ts

@@ -15,6 +15,7 @@ export type { ApplicationApi, ApplicationOutputPorts };
  */
 export function createApplication(
   outputPorts: ApplicationOutputPorts,
+  featureInputs: Readonly<Record<string, unknown>> = {},
 ): ApplicationApi {
   const session = Object.freeze({
     getSnapshot: () => outputPorts.session.getState(),
@@ -107,6 +108,18 @@ export function createApplication(
       }
     },
   });
+  const installedFeatureInputs = Object.freeze({ ...featureInputs });
+  const features = Object.freeze({
+    has(featureId: string) {
+      return Object.hasOwn(installedFeatureInputs, featureId);
+    },
+    get(featureId: string) {
+      if (!Object.hasOwn(installedFeatureInputs, featureId)) {
+        throw new Error(`Application feature is not installed: ${featureId}`);
+      }
+      return installedFeatureInputs[featureId];
+    },
+  });
 
   return Object.freeze({
     session,
@@ -114,5 +127,6 @@ export function createApplication(
     diagnostics,
     runtime,
     recovery,
+    features,
   });
 }