fix: make OCR portable and reliable across AMD64 and ARM64 (#519)

* fix: make OCR portable and reliable

* fix: harden OCR installation portability

* fix: pin OCR partials across downloads

* fix: make OCR execution reliably asynchronous

* fix: harden OCR portability and docs routes

* fix: preserve decoder and docs safeguards

tests/unit/web/custom-async-heartbeat.test.ts

@@ -0,0 +1,64 @@
+// @vitest-environment jsdom
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+import { subscribeEraseObjectJobProgress } from "@/components/tools/erase-object-settings";
+import { subscribeSignPdfJobProgress } from "@/components/tools/sign-pdf-settings";
+
+class FakeEventSource {
+  static OPEN = 1;
+  static instances: FakeEventSource[] = [];
+
+  readonly url: string;
+  readyState = FakeEventSource.OPEN;
+  onmessage: ((event: { data: string }) => void) | null = null;
+  onerror: (() => void) | null = null;
+
+  constructor(url: string) {
+    this.url = url;
+    FakeEventSource.instances.push(this);
+  }
+
+  close() {
+    this.readyState = 2;
+  }
+}
+
+const subscribers = [
+  ["erase-object", subscribeEraseObjectJobProgress],
+  ["sign-pdf", subscribeSignPdfJobProgress],
+] as const;
+
+describe.each(subscribers)("%s async progress", (_name, subscribe) => {
+  beforeEach(() => {
+    vi.useFakeTimers();
+    FakeEventSource.instances = [];
+    vi.stubGlobal("EventSource", FakeEventSource);
+  });
+
+  afterEach(() => {
+    vi.useRealTimers();
+    vi.unstubAllGlobals();
+  });
+
+  it("resets the stall timeout when the server sends a heartbeat", () => {
+    const onStall = vi.fn();
+    const cleanup = subscribe("job-heartbeat", {
+      onComplete: vi.fn(),
+      onFailed: vi.fn(),
+      onStall,
+    });
+
+    expect(FakeEventSource.instances).toHaveLength(1);
+    vi.advanceTimersByTime(4 * 60_000 + 59_000);
+
+    FakeEventSource.instances[0].onmessage?.({
+      data: JSON.stringify({ type: "heartbeat" }),
+    });
+    vi.advanceTimersByTime(2_000);
+
+    expect(onStall).not.toHaveBeenCalled();
+
+    vi.advanceTimersByTime(4 * 60_000 + 59_000);
+    expect(onStall).toHaveBeenCalledOnce();
+    cleanup();
+  });
+});