WIP: Agent/AgentState — 36 errors remaining, all .lock() → .state.lock() or .context.lock()

Bulk replaced Arc<Mutex<Agent>> with Arc<Agent> across all files.
Fixed control.rs, memory.rs tool handlers. Fixed oneshot Backend.
Remaining errors are all agent.lock() → agent.state.lock() or
agent.context.lock() in mind/, user/, and a few in mod.rs.

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

src/user/context.rs

@@ -10,12 +10,12 @@ use super::widgets::{SectionTree, SectionView, section_to_view, pane_block, rend
 use crate::agent::context::{AstNode, NodeBody, Ast};
 
 pub(crate) struct ConsciousScreen {
-    agent: std::sync::Arc<tokio::sync::Mutex<crate::agent::Agent>>,
+    agent: std::sync::Arc<crate::agent::Agent>,
     tree: SectionTree,
 }
 
 impl ConsciousScreen {
-    pub fn new(agent: std::sync::Arc<tokio::sync::Mutex<crate::agent::Agent>>) -> Self {
+    pub fn new(agent: std::sync::Arc<crate::agent::Agent>) -> Self {
         Self { agent, tree: SectionTree::new() }
     }