V0.2.3 - Stable

wtb 0.2.3 fixes the Ray checkpoint skip bug where check_ray_batch_rollback_fork_cache in install_checker.py always skipped with "no checkpoints." The root cause was that graph factory functions defined in main could not be imported by Ray actor processes, causing them to silently fall back to legacy execution without LangGraph checkpointing. This release moves the example graph factory to the importable module wtb.sdk._example_graphs and adds a defense-in-depth cloudpickle serialization fallback in ray_batch_runner.py so that any main-defined factory is automatically serialized and transmitted to actors via Ray's object store. Additionally, actor checkpoint storage is now isolatable per test run via the WTB_RAY_STORAGE_ROOT environment variable, LangGraphStateAdapter.close() now finalizes SQLite WAL files with PRAGMA wal_checkpoint(TRUNCATE) to prevent stale lock files, and BatchExecutionCoordinator.get_checkpoints() logs failures at WARNING level with full tracebacks instead of silently swallowing them at DEBUG.