Fix bounds check panic and batched lock in collect_results

- subconscious.rs: use .get(fork_point..) instead of direct slice
  to avoid panic when fork_point > entries.len()
- dmn.rs: batch all output injections (surface, reflection, thalamus)
  under a single agent lock acquisition instead of three separate ones
- dmn.rs: use Store::cached() instead of Store::load() when rendering
  surfaced memories
- Add scoring persistence analysis notes

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

src/user/subconscious.rs

@@ -166,7 +166,7 @@ impl SubconsciousScreen {
         // Read entries from the forked agent (from fork point onward)
         let entries: Vec<ConversationEntry> = snap.forked_agent.as_ref()
             .and_then(|agent| agent.try_lock().ok())
-            .map(|ag| ag.context.entries[snap.fork_point..].to_vec())
+            .map(|ag| ag.context.entries.get(snap.fork_point..).unwrap_or(&[]).to_vec())
             .unwrap_or_default();
 
         if entries.is_empty() {