fix(js): add typed ChallengeResult interface for PoW worker results

The process() function in fast.ts declared Promise<string> but actually
resolved with the full worker message object { hash, data, difficulty,
nonce }. main.tsx papered over this with `any`. Introduce a shared
ChallengeResult type so the contract between workers, algorithms, and
the main component is enforced by the type checker.

Assisted-by: Claude Opus 4.6 via Claude Code
Signed-off-by: Xe Iaso <me@xeiaso.net>

web/js/algorithms/fast.ts

@@ -1,3 +1,5 @@
+import { ChallengeResult } from "./types";
+
 type ProgressCallback = (nonce: number) => void;
 
 interface ProcessOptions {
@@ -17,7 +19,7 @@ export default function process(
   signal: AbortSignal | null = null,
   progressCallback?: ProgressCallback,
   threads: number = Math.trunc(Math.max(getHardwareConcurrency() / 2, 1)),
-): Promise<string> {
+): Promise<ChallengeResult> {
   console.debug("fast algo");
 
   // Choose worker based on secure context.

web/js/algorithms/index.ts

@@ -1,5 +1,7 @@
 import fast from "./fast";
 
+export type { ChallengeResult } from "./types";
+
 export default {
   fast: fast,
   slow: fast, // XXX(Xe): slow is deprecated, but keep this around in case anything goes bad

web/js/algorithms/types.ts

@@ -0,0 +1,6 @@
+export interface ChallengeResult {
+  hash: string;
+  data: string;
+  difficulty: number;
+  nonce: number;
+}

web/js/main.tsx

@@ -1,6 +1,6 @@
 import { render } from "preact";
 import { useState, useEffect, useRef } from "preact/hooks";
-import algorithms from "./algorithms";
+import algorithms, { ChallengeResult } from "./algorithms";
 
 // from Xeact
 const u = (url: string = "", params: Record<string, any> = {}) => {
@@ -211,7 +211,7 @@ function App({ anubisVersion, basePrefix }: AppProps) {
         }
       },
     )
-      .then((result: any) => {
+      .then((result: ChallengeResult) => {
         const t1 = Date.now();
         const { hash, nonce } = result;