fix(web): make first wasm load work on remote deployment

- Correct engine-manifest single wasm SHA and reuse cache for verification.
- Remove duplicate main-thread wasm fetch; raise init timeout to 300s.
- Record production deployment details and verification evidence.

Co-Authored-By: Claude Code <noreply@anthropic.com>

web/app/src/engine-client/WebEngineClient.ts

@@ -326,7 +326,9 @@ export class WebEngineClient {
   }
 
   async init(): Promise<WebEngineStatus> {
-    return (await this.request({ type: "init" })).status;
+    // The first load fetches and instantiates the multi-hundred-MB engine wasm.
+    // A 30 s budget only fits loopback; remote deployments need a longer first-run window.
+    return (await this.request({ type: "init" }, [], undefined, undefined, undefined, 300_000)).status;
   }
 
   async gpuUICapabilities(): Promise<NonNullable<WebEngineResult["gpuUI"]>> {
@@ -1249,6 +1251,7 @@ export class WebEngineClient {
     onProgress?: (progress: ProgressEvent) => void,
     signal?: AbortSignal,
     nativeInterrupt?: Int32Array,
+    timeoutMs = this.timeoutMs,
   ): Promise<WebEngineResult> {
     if (this.shutdownTask && command.type !== "shutdown" && command.type !== "cancelOpen") return Promise.reject(this.report("INVALID_ARGUMENT", "SESSION_CLOSE_PENDING: native session persistence is in progress", true));
     if (command.type === "openBlend" && signal?.aborted) return Promise.reject(this.report("OPEN_CANCELLED", "Blend open cancelled before dispatch", true));
@@ -1270,7 +1273,7 @@ export class WebEngineClient {
         if (nativeInterrupt && Atomics.load(nativeInterrupt, 0) === 1 && !interruptGraceUsed) {
           interruptGraceUsed = true;
           const pending = this.pending.get(requestId);
-          if (pending) pending.timer = setTimeout(onTimeout, Math.min(this.timeoutMs, 5000));
+          if (pending) pending.timer = setTimeout(onTimeout, Math.min(timeoutMs, 5000));
           return;
         }
         const pending = this.pending.get(requestId);
@@ -1279,9 +1282,9 @@ export class WebEngineClient {
         pending.timedOut = true;
         pending.timeoutError = this.report("WORKER_TERMINATED", `WebEngine 请求超时: ${command.type}`, true);
         pending.cleanup?.(); pending.cleanup = undefined; pending.reject(pending.timeoutError!);
-        pending.timer = setTimeout(() => { if (this.pending.get(requestId) !== pending) return; this.pending.delete(requestId); this.retiredPending.set(requestId, pending); }, this.timeoutMs);
+        pending.timer = setTimeout(() => { if (this.pending.get(requestId) !== pending) return; this.pending.delete(requestId); this.retiredPending.set(requestId, pending); }, timeoutMs);
       };
-      const timer = setTimeout(onTimeout, Math.max(this.timeoutMs,this.renderDeadline-Date.now()));
+      const timer = setTimeout(onTimeout, Math.max(timeoutMs,this.renderDeadline-Date.now()));
       const abort = (): void => {
         void this.request({ type: "cancelOpen", targetRequestId: requestId })
           .catch(() => undefined);