feat(tools): link thoughts and learnings

schema/core.dbml

@@ -32,6 +32,20 @@ Table thought_links {
   }
 }
 
+Table thought_learning_links {
+  id bigserial [pk]
+  thought_id bigint [not null, ref: > thoughts.id]
+  learning_id bigint [not null, ref: > learnings.id]
+  relation text [not null, default: `'source'`]
+  created_at timestamptz [not null, default: `now()`]
+
+  indexes {
+    (thought_id, learning_id) [unique]
+    thought_id
+    learning_id
+  }
+}
+
 Table embeddings {
   id bigserial [pk]
   guid uuid [unique, not null, default: `gen_random_uuid()`]