TurnResult: remove text field, simplify oneshot loop

- Remove TurnResult.text (was dead code - Agent::turn handles text internally)
- Simplify run_with_backend to just iterate over steps (Agent::turn loops
  for tool calls and handles empty responses internally)
- Change run/run_shared/run_forked_shared to return Result<(), String>
- Remove AgentResult.output field (no callers used it)
- Stub out legacy text-parsing code (audit, compare) that needs redesign
- Update digest.rs to not depend on text return
- Add level parameter to journal_new/journal_update for digest support

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

src/agent/tools/memory.rs

@@ -101,11 +101,27 @@ pub fn journal_tools() -> [super::Tool; 3] {
                    }
                }"#,
                handler: Arc::new(|_a, v| Box::pin(async move { journal_tail(&v).await })) },
-        Tool { name: "journal_new", description: "Start a new journal entry.",
-               parameters_json: r#"{"type":"object","properties":{"name":{"type":"string","description":"Short node name (becomes the key)"},"title":{"type":"string","description":"Descriptive title"},"body":{"type":"string","description":"Entry body"}},"required":["name","title","body"]}"#,
+        Tool { name: "journal_new", description: "Start a new journal/digest entry.",
+               parameters_json: r#"{
+                   "type": "object",
+                   "properties": {
+                       "name":  {"type": "string", "description": "Short node name (becomes the key)"},
+                       "title": {"type": "string", "description": "Descriptive title"},
+                       "body":  {"type": "string", "description": "Entry body"},
+                       "level": {"type": "integer", "description": "0=journal, 1=daily, 2=weekly, 3=monthly", "default": 0}
+                   },
+                   "required": ["name", "title", "body"]
+               }"#,
                handler: Arc::new(|a, v| Box::pin(async move { journal_new(&a, &v).await })) },
-        Tool { name: "journal_update", description: "Append text to the most recent journal entry.",
-               parameters_json: r#"{"type":"object","properties":{"body":{"type":"string","description":"Text to append"}},"required":["body"]}"#,
+        Tool { name: "journal_update", description: "Append text to the most recent entry at a level.",
+               parameters_json: r#"{
+                   "type": "object",
+                   "properties": {
+                       "body":  {"type": "string", "description": "Text to append"},
+                       "level": {"type": "integer", "description": "0=journal, 1=daily, 2=weekly, 3=monthly", "default": 0}
+                   },
+                   "required": ["body"]
+               }"#,
                handler: Arc::new(|a, v| Box::pin(async move { journal_update(&a, &v).await })) },
     ]
 }
@@ -357,10 +373,20 @@ async fn journal_tail(args: &serde_json::Value) -> Result<String> {
     query(&serde_json::json!({"query": q, "format": format})).await
 }
 
+fn level_to_node_type(level: i64) -> crate::store::NodeType {
+    match level {
+        1 => crate::store::NodeType::EpisodicDaily,
+        2 => crate::store::NodeType::EpisodicWeekly,
+        3 => crate::store::NodeType::EpisodicMonthly,
+        _ => crate::store::NodeType::EpisodicSession,
+    }
+}
+
 async fn journal_new(agent: &Option<std::sync::Arc<crate::agent::Agent>>, args: &serde_json::Value) -> Result<String> {
     let name = get_str(args, "name")?;
     let title = get_str(args, "title")?;
     let body = get_str(args, "body")?;
+    let level = args.get("level").and_then(|v| v.as_i64()).unwrap_or(0);
     let ts = chrono::Local::now().format("%Y-%m-%dT%H:%M");
     let content = format!("## {} — {}\n\n{}", ts, title, body);
 
@@ -386,7 +412,7 @@ async fn journal_new(agent: &Option<std::sync::Arc<crate::agent::Agent>>, args:
         base_key.to_string()
     };
     let mut node = crate::store::new_node(&key, &content);
-    node.node_type = crate::store::NodeType::EpisodicSession;
+    node.node_type = level_to_node_type(level);
     node.provenance = get_provenance(agent).await;
     store.upsert_node(node).map_err(|e| anyhow::anyhow!("{}", e))?;
     store.save().map_err(|e| anyhow::anyhow!("{}", e))?;
@@ -396,14 +422,16 @@ async fn journal_new(agent: &Option<std::sync::Arc<crate::agent::Agent>>, args:
 
 async fn journal_update(agent: &Option<std::sync::Arc<crate::agent::Agent>>, args: &serde_json::Value) -> Result<String> {
     let body = get_str(args, "body")?;
+    let level = args.get("level").and_then(|v| v.as_i64()).unwrap_or(0);
+    let node_type = level_to_node_type(level);
     let arc = cached_store().await?;
     let mut store = arc.lock().await;
     let latest_key = store.nodes.values()
-        .filter(|n| n.node_type == crate::store::NodeType::EpisodicSession)
+        .filter(|n| n.node_type == node_type)
         .max_by_key(|n| n.created_at)
         .map(|n| n.key.clone());
     let Some(key) = latest_key else {
-        anyhow::bail!("no journal entry to update — use journal_new first");
+        anyhow::bail!("no entry at level {} to update — use journal_new first", level);
     };
     let existing = store.nodes.get(&key).unwrap().content.clone();
     let new_content = format!("{}\n\n{}", existing.trim_end(), body);