Separate identity files (loaded via source: "file" in context_groups)
from the memory store (data_dir). New identity_dir config field,
defaults to ~/.consciousness/identity/.
Also restrict subconscious agents to memory-only tools — no
filesystem write access. This prevents agents from creating stray
.md files in the memory directory.
Co-Authored-By: Proof of Concept <poc@bcachefs.org>