RFC-0026: Runtime ABI v0.2

Status: Normative — frozen for v0.2.0. ABI is C11: little-endian fixed-width scalars, repr(C), no Rust String/Vec/trait/private enum/panic. Every exported function is PweStatus (*fn)(void* user, ..., PweError*); buffers are (const uint8_t* ptr,uint64_t len), output ownership is returned only by runtime_free. RuntimeApi starts u16 major=2,u16 minor,u32 size,void* user; slots in order are world_get, component_view, resource_get, transaction_begin, transaction_submit, handle_release. Caller requires major equality and size covering each used slot; unknown tail slots are ignored. Handles carry type,index,generation and are validated on every call. Each slot documents thread/context constraints in generated C header.