remove dead code: unused imports, functions, and fields

- Remove #![allow(dead_code)] from main.rs, fix all revealed warnings
- Delete unused schema_assimilation() from neuro/scoring.rs
- Delete duplicate memory_dir() wrapper from knowledge.rs
- Deduplicate load_prompt: knowledge.rs now calls neuro::load_prompt
- Remove unused timeout field from DigestLevel
- Remove unused imports (regex::Regex, Provenance, AnyView, Write)
- Mark OldEntry fields as #[allow(dead_code)] (needed for deserialization)

Co-Authored-By: ProofOfConcept <poc@bcachefs.org>

poc-memory/src/query.rs

@@ -21,7 +21,7 @@
 //   key ~ 'journal.*' AND degree > 10 | count
 //   * | sort weight asc | limit 20
 
-use crate::store::{NodeType, Provenance, RelationType, Store};
+use crate::store::{NodeType, RelationType, Store};
 use crate::graph::Graph;
 use regex::Regex;
 use std::collections::BTreeMap;