test(server): align specs with run environment and step schema

- update scenario tests to create runs with required environmentId
- adjust browser controller expectations to session auto-create behavior
- sync playwright/context mocks with current browser service usage

server/test/__mocks__/playwright.ts

@@ -9,6 +9,7 @@ const makePage = () => ({
 
 const makeContext = () => ({
   newPage: jest.fn().mockResolvedValue(makePage()),
+  cookies: jest.fn().mockResolvedValue([]),
   addCookies: jest.fn().mockResolvedValue(undefined),
   addInitScript: jest.fn().mockResolvedValue(undefined),
 });