fix: resolve file library Open File bug, upload reliability, and SSE proxy timeouts (#203)

The Open File button in the Files section did nothing due to a race
condition where the home page reset the file store on mount before files
from handleOpenFile could render. Upload on the files page used fetch
with no timeout, progress, or retry, causing silent failures on mobile
and slow connections. SSE connections for job progress had no keepalive
pings, allowing reverse proxies to kill idle streams.

tests/unit/web/api-extended.test.ts

@@ -216,35 +216,75 @@ describe("apiListFiles", () => {
 // apiUploadUserFiles
 // ==========================================================================
 describe("apiUploadUserFiles", () => {
+  let xhrInstances: Array<Record<string, unknown>>;
+  let OriginalXHR: typeof XMLHttpRequest;
+
   beforeEach(() => {
     fetchMock.mockReset();
     storageMap.clear();
+    xhrInstances = [];
+    OriginalXHR = globalThis.XMLHttpRequest;
+
+    const MockXHR = vi.fn().mockImplementation(() => {
+      const instance: Record<string, unknown> = {
+        open: vi.fn(),
+        send: vi.fn(),
+        setRequestHeader: vi.fn(),
+        upload: {},
+        readyState: 4,
+        status: 200,
+        responseText: "",
+        timeout: 0,
+        onload: null,
+        onerror: null,
+        ontimeout: null,
+      };
+      xhrInstances.push(instance);
+      return instance;
+    });
+    vi.stubGlobal("XMLHttpRequest", MockXHR);
+  });
+
+  afterEach(() => {
+    vi.stubGlobal("XMLHttpRequest", OriginalXHR);
   });
 
   it("sends files as FormData to upload endpoint", async () => {
     const file = new File(["content"], "img.png", { type: "image/png" });
-    fetchMock.mockReturnValueOnce(
-      okJson({ files: [{ id: "1", originalName: "img.png", size: 7, version: 1 }] }),
-    );
+    const responseData = { files: [{ id: "1", originalName: "img.png", size: 7, version: 1 }] };
 
-    const result = await apiUploadUserFiles([file]);
-    expect(fetchMock.mock.calls[0][0]).toBe("/api/v1/files/upload");
-    expect(fetchMock.mock.calls[0][1].method).toBe("POST");
+    const promise = apiUploadUserFiles([file]);
+    const xhr = xhrInstances[0];
+    expect(xhr.open).toHaveBeenCalledWith("POST", "/api/v1/files/upload");
+
+    xhr.status = 200;
+    xhr.responseText = JSON.stringify(responseData);
+    (xhr.onload as () => void)();
+
+    const result = await promise;
     expect(result.files).toHaveLength(1);
   });
 
   it("throws on non-ok response", async () => {
     const file = new File(["content"], "img.png", { type: "image/png" });
-    fetchMock.mockReturnValueOnce(
-      Promise.resolve({ ok: false, status: 413, json: () => Promise.reject(new Error("no")) }),
-    );
-    await expect(apiUploadUserFiles([file])).rejects.toThrow("Upload failed: 413");
+
+    const promise = apiUploadUserFiles([file]);
+    const xhr = xhrInstances[0];
+    xhr.status = 413;
+    xhr.responseText = "";
+    (xhr.onload as () => void)();
+
+    await expect(promise).rejects.toThrow("Upload failed: 413");
   });
 
-  it("triggers disconnected on TypeError", async () => {
+  it("triggers disconnected on network error", async () => {
     const file = new File(["content"], "img.png", { type: "image/png" });
-    fetchMock.mockRejectedValueOnce(new TypeError("Failed to fetch"));
-    await expect(apiUploadUserFiles([file])).rejects.toThrow("Failed to fetch");
+
+    const promise = apiUploadUserFiles([file]);
+    const xhr = xhrInstances[0];
+    (xhr.onerror as () => void)();
+
+    await expect(promise).rejects.toThrow("Network error");
   });
 });