FN-6078: fix dashboard tests to use constructable mocks

Update dashboard tests to mirror constructor-based browser APIs and xterm addons.

- rewrite SessionTerminal mobile test doubles as constructable function mocks so xterm and addon instances initialize like real classes
- replace the useDocuments AbortController stub with a class-based mock to preserve constructor semantics during fetch cancellation tests

Files changed:
 .../__tests__/SessionTerminal.mobile.test.tsx       | 21 +++++++++++++++++----
 .../app/hooks/__tests__/useDocuments.test.ts        |  8 ++++----
 2 files changed, 21 insertions(+), 8 deletions(-)

Fusion-Task-Id: FN-6078

Fusion-Task-Lineage: d8e0a9aa-6c7c-44c1-b9d4-5196924531c1

packages/dashboard/app/components/__tests__/SessionTerminal.mobile.test.tsx

@@ -13,11 +13,24 @@ const mockTerm = {
   cols: 80,
   rows: 24,
 };
-vi.mock("@xterm/xterm", () => ({ Terminal: vi.fn(() => mockTerm) }));
-vi.mock("@xterm/addon-fit", () => ({ FitAddon: vi.fn(() => ({ fit: vi.fn() })) }));
-vi.mock("@xterm/addon-unicode11", () => ({ Unicode11Addon: vi.fn(() => ({})) }));
+vi.mock("@xterm/xterm", () => ({
+  Terminal: vi.fn(function (this: typeof mockTerm) {
+    Object.assign(this, mockTerm);
+  }),
+}));
+vi.mock("@xterm/addon-fit", () => ({
+  FitAddon: vi.fn(function (this: { fit: ReturnType<typeof vi.fn> }) {
+    this.fit = vi.fn();
+  }),
+}));
+vi.mock("@xterm/addon-unicode11", () => ({
+  Unicode11Addon: vi.fn(function () {}),
+}));
 vi.mock("@xterm/addon-webgl", () => ({
-  WebglAddon: vi.fn(() => ({ onContextLoss: vi.fn(), dispose: vi.fn() })),
+  WebglAddon: vi.fn(function (this: { onContextLoss: ReturnType<typeof vi.fn>; dispose: ReturnType<typeof vi.fn> }) {
+    this.onContextLoss = vi.fn();
+    this.dispose = vi.fn();
+  }),
 }));
 
 const apiMock = vi.fn();

packages/dashboard/app/hooks/__tests__/useDocuments.test.ts

@@ -228,10 +228,10 @@ describe("useDocuments", () => {
     const abortMock = vi.fn();
     const originalAbortController = globalThis.AbortController;
 
-    globalThis.AbortController = vi.fn().mockImplementation(() => ({
-      signal: {},
-      abort: abortMock,
-    })) as unknown as typeof AbortController;
+    globalThis.AbortController = class {
+      signal = {};
+      abort = abortMock;
+    } as unknown as typeof AbortController;
 
     globalThis.fetch = vi.fn().mockReturnValue(
       new Promise(() => {