feat(KB-648): enable parallel test execution and optimize test performance

- Optimize backup tests using fake timers instead of real timeouts

- Enable parallel file execution in core, engine, CLI, and dashboard packages

- Add inline test helpers to reduce dependencies in dashboard routes tests

- Update executor tests with exact command matching and improved assertions

- Update AGENTS.md with test optimization patterns (fake timers, unique temp dirs)

packages/dashboard/app/components/__tests__/GitManagerModal.test.tsx

@@ -991,9 +991,8 @@ describe("GitManagerModal", () => {
     await user.clear(nameInput);
     await user.type(nameInput, "upstream");
 
-    const saveButton = nameInput.closest(".gm-remote-edit")?.querySelector(".btn.btn-sm.btn-primary");
-    expect(saveButton).toBeTruthy();
-    await user.click(saveButton as HTMLButtonElement);
+    const saveButton = screen.getByRole("button", { name: "" }); // Check button
+    await user.click(saveButton);
 
     await waitFor(() => {
       expect(renameGitRemote).toHaveBeenCalledWith("origin", "upstream");
@@ -1024,9 +1023,8 @@ describe("GitManagerModal", () => {
     await user.clear(urlInput);
     await user.type(urlInput, "https://new-url.com/repo.git");
 
-    const saveButton = urlInput.closest(".gm-remote-edit")?.querySelector(".btn.btn-sm.btn-primary");
-    expect(saveButton).toBeTruthy();
-    await user.click(saveButton as HTMLButtonElement);
+    const saveButton = screen.getByRole("button", { name: "" }); // Check button
+    await user.click(saveButton);
 
     await waitFor(() => {
       expect(updateGitRemoteUrl).toHaveBeenCalledWith("origin", "https://new-url.com/repo.git");