TranscriptInfo provides cached transcript metadata (path, size)
with a single read. Replaces scattered fs::metadata calls in
surface_observe_cycle, reflection_cycle, resolve_conversation,
and resolve_memory_ratio.
Session::transcript() resolves the path from transcript_path or
by searching projects dir, returning a TranscriptInfo.
Co-Authored-By: Kent Overstreet <kent.overstreet@linux.dev>
Generic session state (session_id, seen set, state directory) doesn't
belong in the memory search module. Now at crate root, re-exported
from memory_search for backwards compatibility.
Co-Authored-By: Proof of Concept <poc@bcachefs.org>
