training: per-node scoring with graph weight updates

Memory scoring now uses the graph as source of truth:
- last_scored timestamp on each node (new capnp field @22)
- Nodes scored when older than scoring_interval_secs (default 1hr)
- Oldest-scored-first ordering
- Window: scoring_response_window assistant responses (default 100)
- First-quarter memories scored even without full window
- Per-response normalization (raw divergence / response count)
- Asymmetric weight update: alpha=0.5 up, alpha=0.1 down
  (responds fast to importance, decays slowly — memories stay
  surfaced even if only useful 1/4 of the time)

Graph writes disabled pending normalization calibration.

Also: configurable scoring_interval_secs and scoring_response_window.

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

src/agent/mod.rs

@@ -662,13 +662,19 @@ impl Agent {
                         _ => unreachable!(),
                     };
                     let text = entry.message().content_text();
-                    let score = memory_scores
+                    // Show node weight from graph (updated by incremental scorer)
+                    let graph_weight = crate::hippocampus::store::Store::load().ok()
+                        .and_then(|s| s.nodes.get(key).map(|n| n.weight));
+                    // Show full matrix score if available
+                    let matrix_score = memory_scores
                         .and_then(|s| s.memory_weights.iter()
                             .find(|(k, _)| k == key)
                             .map(|(_, v)| *v));
-                    let label = match score {
-                        Some(v) => format!("{} (importance: {:.1})", key, v),
-                        None => key.to_string(),
+                    let label = match (graph_weight, matrix_score) {
+                        (Some(w), Some(s)) => format!("{} (w:{:.2} score:{:.1})", key, w, s),
+                        (Some(w), None) => format!("{} (w:{:.2})", key, w),
+                        (None, Some(s)) => format!("{} (score:{:.1})", key, s),
+                        (None, None) => key.to_string(),
                     };
                     ContextSection {
                         name: label,