AI-assisted testing, extensions updates, and more: k6 2.0 is here

k6 2.0 is now generally available, introducing AI-assisted testing workflows, a new Assertions API, expanded Playwright compatibility in the browser module, and major extensions updates. New CLI commands (`k6 x agent`, `k6 x mcp`, `k6 x docs`, `k6 x explore`) enable integration with AI coding assistants like Claude Code, Cursor, and Codex via MCP. The release also consolidates official and community extensions into a single catalog, upgrades xk6 into a full extension development toolbox, adds subcommand extensions, introduces structured JSON summary output for CI/CD and AI agents, native OpenTelemetry output, and promotes k6 Operator 1.0 to stable for distributed Kubernetes-based load testing.