query: unify PEG and engine parsers

PEG parser now handles both expression syntax (degree > 5 | sort degree)
and pipeline syntax (all | type:episodic | sort:timestamp). Deleted
Stage::parse() and helpers from engine.rs — it's now pure execution.

All callers use parse_stages() from parser.rs as the single entry point.

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

src/agent/tools/memory.rs

@@ -260,7 +260,7 @@ async fn query(args: &serde_json::Value) -> Result<String> {
     let store = arc.lock().await;
     let graph = store.build_graph();
 
-    let stages = crate::search::Stage::parse_pipeline(query_str)
+    let stages = crate::query_parser::parse_stages(query_str)
         .map_err(|e| anyhow::anyhow!("{}", e))?;
     let results = crate::search::run_query(&stages, vec![], &graph, &store, false, 100);
     let keys: Vec<String> = results.into_iter().map(|(k, _)| k).collect();
@@ -272,12 +272,61 @@ async fn query(args: &serde_json::Value) -> Result<String> {
             Ok(crate::subconscious::prompts::format_nodes_section(&store, &items, &graph))
         }
         _ => {
-            crate::query_parser::query_to_string(&store, &graph, query_str)
-                .map_err(|e| anyhow::anyhow!("{}", e))
+            // Compact output: check for count/select stages, else just list keys
+            use crate::search::{Stage, Transform};
+            let has_count = stages.iter().any(|s| matches!(s, Stage::Transform(Transform::Count)));
+            if has_count {
+                return Ok(keys.len().to_string());
+            }
+            if keys.is_empty() {
+                return Ok("no results".to_string());
+            }
+            let select_fields: Option<&Vec<String>> = stages.iter().find_map(|s| match s {
+                Stage::Transform(Transform::Select(f)) => Some(f),
+                _ => None,
+            });
+            if let Some(fields) = select_fields {
+                let mut out = String::from("key\t");
+                out.push_str(&fields.join("\t"));
+                out.push('\n');
+                for key in &keys {
+                    out.push_str(key);
+                    for f in fields {
+                        out.push('\t');
+                        out.push_str(&resolve_field_str(&store, &graph, key, f));
+                    }
+                    out.push('\n');
+                }
+                Ok(out)
+            } else {
+                Ok(keys.join("\n"))
+            }
         }
     }
 }
 
+fn resolve_field_str(store: &crate::store::Store, graph: &crate::graph::Graph, key: &str, field: &str) -> String {
+    let node = match store.nodes.get(key) {
+        Some(n) => n,
+        None => return "-".to_string(),
+    };
+    match field {
+        "key"           => key.to_string(),
+        "weight"        => format!("{:.3}", node.weight),
+        "node_type"     => format!("{:?}", node.node_type),
+        "provenance"    => node.provenance.clone(),
+        "emotion"       => format!("{}", node.emotion),
+        "retrievals"    => format!("{}", node.retrievals),
+        "uses"          => format!("{}", node.uses),
+        "wrongs"        => format!("{}", node.wrongs),
+        "created"       => format!("{}", node.created_at),
+        "timestamp"     => format!("{}", node.timestamp),
+        "degree"        => format!("{}", graph.degree(key)),
+        "content_len"   => format!("{}", node.content.len()),
+        _ => "-".to_string(),
+    }
+}
+
 // ── Journal tools ──────────────────────────────────────────────
 
 async fn journal_tail(args: &serde_json::Value) -> Result<String> {