Memory tool results (memory_render) are now pushed as
ConversationEntry::Memory with the node key, instead of plain
Messages. Remove loaded_nodes from ContextState — the debug
screen reads memory info from Memory entries in the conversation.
Surfaced memories from surface-observe are pushed as separate
Memory entries, reflections as separate system-reminder messages.
User input is no longer polluted with hook output.
Co-Authored-By: Proof of Concept <poc@bcachefs.org>