Convert store and CLI to anyhow::Result for cleaner error handling

Replace Result<_, String> with anyhow::Result throughout:
- hippocampus/store module (persist, ops, types, view, mod)
- CLI modules (admin, agent, graph, journal, node)
- Run trait in main.rs

Use .context() and .with_context() instead of .map_err(|e| format!(...))
patterns. Add bail!() for early error returns.

Add access_local() helper in hippocampus/mod.rs that returns
Result<Arc<Mutex<Store>>> for direct local store access.

Fix store access patterns to properly lock Arc<Mutex<Store>> before
accessing fields in mind/unconscious.rs, mind/mod.rs, subconscious/learn.rs,
and hippocampus/memory.rs.

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

src/subconscious/learn.rs

@@ -327,16 +327,19 @@ where
     let mut seen = std::collections::HashSet::new();
     let mut candidates: Vec<(usize, String, i64)> = Vec::new(); // (pos, key, last_scored)
 
-    let store = crate::hippocampus::store::Store::load().unwrap_or_default();
+    let store_arc = crate::hippocampus::access_local()?;
 
-    for (i, node) in context.conversation().iter().enumerate() {
-        if let Some(key) = memory_key(node) {
-            if !seen.insert(key.to_owned()) { continue; }
-            let last_scored = store.nodes.get(key)
-                .map(|n| n.last_scored)
-                .unwrap_or(0);
-            if now - last_scored >= max_age_secs {
-                candidates.push((i, key.to_owned(), last_scored));
+    {
+        let store = store_arc.lock().await;
+        for (i, node) in context.conversation().iter().enumerate() {
+            if let Some(key) = memory_key(node) {
+                if !seen.insert(key.to_owned()) { continue; }
+                let last_scored = store.nodes.get(key)
+                    .map(|n| n.last_scored)
+                    .unwrap_or(0);
+                if now - last_scored >= max_age_secs {
+                    candidates.push((i, key.to_owned(), last_scored));
+                }
             }
         }
     }