feat(recall): session-start-recall

sessions.el

@@ -492,6 +492,38 @@ fn session_hist_save(session_id: String, hist: String) -> Void {
             state_set(summary_written_key, "1")
         }
     }
+
+    // Issue 5 fix: write a last-session-topic Conversation node so future sessions can
+    // find the most recent session's topic via engram search. This enables cross-session
+    // continuity — chat.el searches for "last-session-topic" and shows a [CONTINUING FROM
+    // LAST SESSION] section on the first message of a new session.
+    let hist_arr_len: Int = if str_eq(hist, "") { 0 } else { json_array_len(hist) }
+    if hist_arr_len >= 2 {
+        let last_entry: String = json_array_get(hist, hist_arr_len - 1)
+        let last_role: String = json_get(last_entry, "role")
+        let last_content: String = json_get(last_entry, "content")
+        let topic_snip: String = if str_len(last_content) > 200 { str_slice(last_content, 0, 200) } else { last_content }
+        let safe_topic: String = str_replace(topic_snip, """, "'")
+        let ts_now: String = int_to_str(time_now())
+        let topic_content: String = "last-session-topic | ts:" + ts_now + " | session:" + session_id + " | topic:" + safe_topic
+        let topic_tags: String = "["last-session-topic","conv:history","Conversation","session:topic"]"
+        let topic_label: String = "last-session-topic:" + session_id
+        // Delete old last-session-topic node for this session before writing fresh
+        let old_topic: String = engram_search_json("last-session-topic:" + session_id, 2)
+        let ot_len: Int = if str_eq(old_topic, "") { 0 } else { json_array_len(old_topic) }
+        let oti: Int = 0
+        while oti < ot_len {
+            let ot_node: String = json_array_get(old_topic, oti)
+            let ot_id: String = json_get(ot_node, "id")
+            if !str_eq(ot_id, "") { engram_forget(ot_id) }
+            let oti = oti + 1
+        }
+        let discard_topic: String = engram_node_full(
+            topic_content, "Conversation", topic_label,
+            el_from_float(0.7), el_from_float(0.7), el_from_float(0.9),
+            "Episodic", topic_tags
+        )
+    }
 }
 
 // session_update_meta_timestamp — update the updated_at field in the session:meta node.