Release 0.4.0

Added

Streaming Support

• Executor.stream() - New async generator method for streaming module execution
• Implements same 6-step pipeline as call_async() (context, safety, lookup, ACL, input validation, middleware before)
• Falls back to call_async() yielding single chunk for non-streaming modules
• For streaming modules, iterates module.stream() and yields each chunk
• Accumulates chunks via shallow merge for output validation and after-middleware
• Full error handling with middleware recovery
• ModuleAnnotations.streaming - New streaming: bool = False field to indicate if a module supports streaming execution
• Test coverage - Added 5 comprehensive tests in test_executor_stream.py:
• Fallback behavior for non-streaming modules
• Multi-chunk streaming
• Module not found error handling
• Before/after middleware integration
• Disjoint key accumulation via shallow merge