Wotan Memory Protocol for the Unheaded Protocol

Wotan is the memory and I/O bus for the Unheaded Protocol, providing addressable per-flow storage for BPF programs executing within the Limited Domain. The Wotan protocol specifies the BPF helper interface for memory access, the address space layout for per-flow data structures, a five-level cache hierarchy (L0 through L4), and the topic-based I/O model for interaction with userspace services. This memo defines the memory model, helper functions, address space, cache miss protocol, gRPC streaming contracts, triple-role architecture, reliability guarantees, and I/O topic naming conventions for systems implementing the Unheaded Protocol's computational layer. Draft-03 introduces a structured error code taxonomy with severity levels, helper return codes for common operations, and error recovery procedures. Draft-02 security patches W1-W8 are retained.