Init Axo design system

ts/axo/_internal/assert.tsx

@@ -0,0 +1,17 @@
+// Copyright 2025 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+export class AssertionError extends TypeError {
+  override name = 'AssertionError';
+}
+
+export function assert(condition: boolean, message?: string): asserts condition;
+export function assert<T>(input: T, message?: string): NonNullable<T>;
+export function assert<T>(input: T, message?: string): NonNullable<T> {
+  if (input === false || input == null) {
+    // eslint-disable-next-line no-debugger
+    debugger;
+    throw new AssertionError(message ?? `input is ${input}`);
+  }
+  return input;
+}