Remove Store::cached(), consolidate on access_local()

- Remove CACHED_STORE, cached(), is_stale(), set_store() - redundant
- Convert all Store::cached() callers to use access_local()
- Single Store::load() call remains in access() fallback path

All store access now goes through hippocampus::access() / access_local(),
which handles socket connection or local fallback with caching.

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

src/hippocampus/mod.rs

@@ -44,14 +44,9 @@ pub enum StoreAccess {
     None(String),                       // Error: couldn't get access
 }
 
-/// Set the global store handle. Call once at daemon startup (eager init).
-pub fn set_store(store: Arc<crate::Mutex<Store>>) {
-    STORE_ACCESS.set(Some(store)).ok();
-}
-
 /// Get store access: daemon's store, socket, or local fallback.
 pub fn access() -> StoreAccess {
-    // Daemon: already set via set_store()
+    // Check if already cached
     if let Some(Some(store)) = STORE_ACCESS.get() {
         return StoreAccess::Daemon(store.clone());
     }