store: remove visit tracking infrastructure

Remove AgentVisit, TranscriptSegment, and all related visit tracking code.
Provenance is what we've been using to track agent interaction with nodes.

Also removes dead fields from Node (state_tag, created).

-349 lines.

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

src/cli/agent.rs

@@ -39,23 +39,18 @@ pub async fn cmd_run_agent(agent: &str, count: usize, target: &[String], query:
         vec![] // use agent's built-in query
     };
 
-    let arc = memory::access_local()?;
-
     if !resolved_targets.is_empty() {
         for (i, key) in resolved_targets.iter().enumerate() {
             println!("[{}] [{}/{}] {}", agent, i + 1, resolved_targets.len(), key);
-            let mut store = arc.lock().await;
             if let Err(e) = crate::agent::oneshot::run_one_agent(
-                &mut store, agent, count, Some(&[key.clone()]),
+                agent, count, Some(&[key.clone()]),
             ).await {
                 println!("[{}] ERROR on {}: {}", agent, key, e);
             }
         }
     } else {
-        // Local execution (--local, --debug, dry-run, or daemon unavailable)
-        let mut store = arc.lock().await;
         crate::agent::oneshot::run_one_agent(
-            &mut store, agent, count, None,
+            agent, count, None,
         ).await.map_err(|e| anyhow::anyhow!("{}", e))?;
     }
     Ok(())