API: Add weakenEffect to formulas.hacking namespace (#2626)

src/ScriptEditor/NetscriptDefinitions.d.ts

@@ -6299,6 +6299,16 @@ interface HackingFormulas {
    * @returns The calculated weaken time, in milliseconds.
    */
   weakenTime(server: Server, player: Person): number;
+  /**
+   * Calculate the security decrease from a weaken operation.
+   * Unlike other hacking formulas, weaken effect depends only on thread count and
+   * core count, not on server or player properties. The core bonus formula is
+   * {@code 1 + (cores - 1) / 16}.
+   * @param threads - Number of threads running weaken.
+   * @param cores - Number of cores on the host server. Default 1.
+   * @returns The security decrease amount.
+   */
+  weakenEffect(threads: number, cores?: number): number;
 }
 
 /**