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/daemon.rs

@@ -338,7 +338,7 @@ pub fn run_daemon() -> Result<(), String> {
 
             // Load fact-mined keys too
             let fact_keys: HashSet<String> = {
-                use crate::store::{AnyView, StoreView};
+                use crate::store::StoreView;
                 let view = crate::store::AnyView::load().ok();
                 view.map(|v| {
                     let mut keys = HashSet::new();