show scoring progress and per-response memory attribution

Status bar shows "scoring 3/7..." during scoring. Debug pane logs
per-memory importance and top-5 response breakdowns. F10 context
screen shows which memories were important for each assistant
response as drilldown children (← memory_key (score)).

Added important_memories_for_entry() to look up the matrix by
conversation entry index.

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

src/agent/runner.rs

@@ -739,11 +739,27 @@ impl Agent {
                         Role::System => "system".to_string(),
                     }
                 };
+                // Show which memories were important for this response
+                let children = if m.role == Role::Assistant {
+                    self.memory_scores.as_ref()
+                        .map(|s| s.important_memories_for_entry(i))
+                        .unwrap_or_default()
+                        .into_iter()
+                        .map(|(key, score)| ContextSection {
+                            name: format!("← {} ({:.1})", key, score),
+                            tokens: 0,
+                            content: String::new(),
+                            children: Vec::new(),
+                        })
+                        .collect()
+                } else {
+                    Vec::new()
+                };
                 ContextSection {
                     name: format!("[{}] {}: {}", i, role_name, label),
                     tokens,
                     content: text,
-                    children: Vec::new(),
+                    children,
                 }
             })
             .collect();