fix(openapi):validate API spec imports (#8322)

* fix(openapi):validate API spec imports and resolve preview to error state instead of hanging

* fix(openapi):allows opening of malformed files with correct extension

* fix(openapi):reject non-OpenAPI content in spec preview before timeout

* test(openapi): add unit + e2e coverage for spec import validation

* refactor(openapi):centralise spec error messages and fix dialog restore

* fix:removed nested try catch

* test:added common locators

* refactor:removed repeated lines

* refactor:removed redundant file reads

---------

Co-authored-by: Adwait Aayush <adwaitaayush@Adwaits-MacBook-Air.local>

tests/utils/page/openapi/render-spec.ts

@@ -0,0 +1,30 @@
+import { test, Page, ElectronApplication } from '../../../../playwright';
+
+export const buildApiSpecPanelLocators = (page: Page) => ({
+  addMenuButton: () => page.getByTestId('api-specs-header-add-menu'),
+  openApiSpecMenuItem: () => page.getByTestId('api-specs-header-add-menu-open-api-spec'),
+  sidebarItem: (name: string) => page.locator('.api-spec-item').filter({ hasText: name })
+});
+
+export const openApiSpecFromDialog = async (
+  page: Page,
+  electronApp: ElectronApplication,
+  filePath: string
+): Promise<void> => {
+  await test.step(`Open API spec from path: ${filePath}`, async () => {
+    await electronApp.evaluate(({ dialog }, filePath) => {
+      dialog.showOpenDialog = async () => ({ canceled: false, filePaths: [filePath] });
+    }, filePath);
+
+    const { addMenuButton, openApiSpecMenuItem } = buildApiSpecPanelLocators(page);
+    await addMenuButton().click();
+    await openApiSpecMenuItem().click();
+  });
+};
+
+export const openApiSpecSidebarItem = async (page: Page, name: string): Promise<void> => {
+  await test.step(`Open API spec sidebar item "${name}"`, async () => {
+    const { sidebarItem } = buildApiSpecPanelLocators(page);
+    await sidebarItem(name).click();
+  });
+};