relations: bulk lifecycle — relate-many! + unrelate-node! cascade cleanup + 12 tests

unrelate-node! retracts every local edge touching a node (all kinds, both
directions); leaves federated peer links alone. 147/147.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/relations/api.sx

@@ -100,3 +100,42 @@
 (define
   relations/connected?
   (fn (a b kind) (relations-connected? (relations-ensure-db!) a b kind)))
+
+(define
+  relations-relate-many!
+  (fn
+    (db triples)
+    (do
+      (for-each
+        (fn
+          (t)
+          (dl-assert!
+            db
+            (relations-rel (first t) (nth t 1) (nth t 2))))
+        triples)
+      db)))
+
+(define
+  relations-unrelate-node!
+  (fn
+    (db node)
+    (do
+      (for-each
+        (fn
+          (s)
+          (dl-retract! db (relations-rel node (get s :Dst) (get s :Kind))))
+        (dl-query db (list (quote rel) node (quote Dst) (quote Kind))))
+      (for-each
+        (fn
+          (s)
+          (dl-retract! db (relations-rel (get s :Src) node (get s :Kind))))
+        (dl-query db (list (quote rel) (quote Src) node (quote Kind))))
+      db)))
+
+(define
+  relations/relate-many!
+  (fn (triples) (relations-relate-many! (relations-ensure-db!) triples)))
+
+(define
+  relations/unrelate-node!
+  (fn (node) (relations-unrelate-node! (relations-ensure-db!) node)))