use new createContext utility for better type safety

packages/svelte/src/lib/store/context.ts

@@ -0,0 +1,36 @@
+import type { ConnectableContext } from '$lib/components/NodeWrapper/types';
+import { setContext, getContext, hasContext } from 'svelte';
+import type { StoreContext } from './types';
+
+/**
+ * Creates a type-safe context getter and setter pair.
+ * Extended from Svelte's official createContext pattern.
+ * - When called with an error message string, it throws if the context is not set
+ * - When called without arguments, it returns the context value or undefined
+ */
+function createContext<T>(): [
+  {
+    (errorMessage: string): T;
+    (): T | undefined;
+  },
+  (context: T) => T
+] {
+  const key = {};
+
+  return [
+    (errorMessage?: string) => {
+      if (errorMessage && !hasContext(key)) {
+        throw new Error(errorMessage);
+      }
+
+      return getContext(key);
+    },
+    (context) => setContext(key, context)
+  ];
+}
+
+export const [getNodeIdContext, setNodeIdContext] = createContext<string>();
+export const [getNodeConnectableContext, setNodeConnectableContext] =
+  createContext<ConnectableContext>();
+
+export const [getEdgeIdContext, setEdgeIdContext] = createContext<string>();