Feat: simplify vault API and update docs

vault/src/session.rs

@@ -1,22 +1,4 @@
 //! Session manager for the vault crate (optional)
 
-use crate::data::KeyspaceData;
-use std::collections::HashMap;
 
-pub struct SessionManager {
-    unlocked_keyspaces: HashMap<String, KeyspaceData>,
-    current_keyspace: Option<String>,
-    current_keypair: Option<String>,
-    // ...
-}
 
-impl SessionManager {
-    pub fn new() -> Self {
-        Self {
-            unlocked_keyspaces: HashMap::new(),
-            current_keyspace: None,
-            current_keypair: None,
-        }
-    }
-    // ... methods for unlock, lock, select, timeout, etc.
-}