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/hippocampus/store/view.rs

@@ -6,6 +6,7 @@
 
 use super::types::*;
 
+use anyhow::Result;
 use std::fs;
 
 // ---------------------------------------------------------------------------
@@ -186,7 +187,7 @@ pub enum AnyView {
 
 impl AnyView {
     /// Load the fastest available view: mmap snapshot or owned store.
-    pub fn load() -> Result<Self, String> {
+    pub fn load() -> Result<Self> {
         if let Some(mv) = MmapView::open() {
             Ok(AnyView::Mmap(mv))
         } else {