fix(rules-injector): cache directory scan results per session

src/hooks/rules-injector/rule-scan-cache.ts

@@ -0,0 +1,21 @@
+export type RuleScanCache = {
+  get: (key: string) => string[] | undefined;
+  set: (key: string, value: string[]) => void;
+  clear: () => void;
+};
+
+export function createRuleScanCache(): RuleScanCache {
+  const cache = new Map<string, string[]>();
+
+  return {
+    get(key: string): string[] | undefined {
+      return cache.get(key);
+    },
+    set(key: string, value: string[]): void {
+      cache.set(key, value);
+    },
+    clear(): void {
+      cache.clear();
+    },
+  };
+}