context: heal pre-refactor image logs with token_count=0

Recompute image token counts from persisted dimensions when loading
old logs that stored count=0 (server-authoritative count was applied
after AppendImage before client-side pad expansion).

graph: cache neighbor sets for clustering coefficient

Pre-compute neighbor HashSets so the O(deg^2) triangle-counting
inner loop doesn't re-allocate on every (i,j) pair. avg_clustering_
coefficient() now builds the cache once instead of O(N*deg) times.

src/agent/context.rs

@@ -125,7 +125,19 @@ impl<'de> Deserialize<'de> for NodeLeaf {
             body: NodeBody,
             timestamp: DateTime<Utc>,
         }
-        let raw = Raw::deserialize(deserializer)?;
+        let mut raw = Raw::deserialize(deserializer)?;
+        // Heal pre-refactor logs: Image leaves used to be deserialized
+        // with token_count=0 (server-authoritative count was applied
+        // after AppendImage). With pads now expanded client-side at
+        // construction, recompute from the persisted dimensions if
+        // the stored count is 0.
+        if let NodeBody::Image { orig_height, orig_width, token_count, .. }
+            = &mut raw.body
+        {
+            if *token_count == 0 {
+                *token_count = qwen3_image_token_count(*orig_height, *orig_width);
+            }
+        }
         let token_ids = raw.body.compute_token_ids();
         Ok(NodeLeaf { body: raw.body, token_ids, timestamp: raw.timestamp })
     }

src/hippocampus/graph.rs

@@ -40,6 +40,31 @@ pub struct Graph {
     communities: HashMap<String, u32>,
 }
 
+/// Compute clustering coefficient for a node whose neighbor-set is `nbrs`,
+/// using `cache` to look up each neighbor's neighbor-set in O(1) without
+/// re-allocating on every (i, j) pair of the inner loop.
+fn cc_cached<'a>(
+    nbrs: &HashSet<&'a str>,
+    cache: &HashMap<&'a str, HashSet<&'a str>>,
+) -> f32 {
+    let deg = nbrs.len();
+    if deg < 2 {
+        return 0.0;
+    }
+    let neighbor_vec: Vec<&str> = nbrs.iter().copied().collect();
+    let mut triangles = 0u32;
+    for i in 0..neighbor_vec.len() {
+        for j in (i + 1)..neighbor_vec.len() {
+            if let Some(ni) = cache.get(neighbor_vec[i]) {
+                if ni.contains(neighbor_vec[j]) {
+                    triangles += 1;
+                }
+            }
+        }
+    }
+    (2.0 * triangles as f32) / (deg as f32 * (deg as f32 - 1.0))
+}
+
 impl Graph {
     pub fn nodes(&self) -> &HashSet<String> {
         &self.keys
@@ -207,34 +232,37 @@ impl Graph {
     /// cc(v) = 2E / (deg * (deg - 1))
     pub fn clustering_coefficient(&self, key: &str) -> f32 {
         let neighbors = self.neighbor_keys(key);
-        let deg = neighbors.len();
-        if deg < 2 {
+        if neighbors.len() < 2 {
             return 0.0;
         }
-
-        let neighbor_vec: Vec<&str> = neighbors.iter().copied().collect();
-        let mut triangles = 0u32;
-        for i in 0..neighbor_vec.len() {
-            for j in (i + 1)..neighbor_vec.len() {
-                let ni_neighbors = self.neighbor_keys(neighbor_vec[i]);
-                if ni_neighbors.contains(neighbor_vec[j]) {
-                    triangles += 1;
-                }
-            }
-        }
-
-        (2.0 * triangles as f32) / (deg as f32 * (deg as f32 - 1.0))
+        // Cache each neighbor's neighbor-set so the O(deg^2) inner loop
+        // doesn't re-allocate a HashSet on every (i, j) pair.
+        let cache: HashMap<&str, HashSet<&str>> = neighbors
+            .iter()
+            .map(|&n| (n, self.neighbor_keys(n)))
+            .collect();
+        cc_cached(&neighbors, &cache)
     }
 
     /// Average clustering coefficient across all nodes with deg >= 2
     pub fn avg_clustering_coefficient(&self) -> f32 {
+        // Pre-compute neighbor sets for the whole graph once so we don't
+        // rebuild O(N * deg) HashSets across the outer loop.
+        let cache: HashMap<&str, HashSet<&str>> = self
+            .keys
+            .iter()
+            .map(|k| (k.as_str(), self.neighbor_keys(k)))
+            .collect();
+
         let mut sum = 0.0f32;
         let mut count = 0u32;
         for key in &self.keys {
-            if self.degree(key) >= 2 {
-                sum += self.clustering_coefficient(key);
-                count += 1;
-            }
+            let nbrs = match cache.get(key.as_str()) {
+                Some(s) if s.len() >= 2 => s,
+                _ => continue,
+            };
+            sum += cc_cached(nbrs, &cache);
+            count += 1;
         }
         if count == 0 { 0.0 } else { sum / count as f32 }
     }