Fix polling interval leak on SPA navigation

The poll trigger in bind-triggers called set-interval but discarded the
interval ID, so polls continued firing after the element was removed from
the DOM. Now the callback checks el.isConnected each tick and self-clears
when the element is gone (HTMX-style cleanup).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

shared/static/wasm/sx/orchestration.sx

@@ -410,9 +410,20 @@
               (mods (get trigger "modifiers")))
             (cond
               (= kind "poll")
-              (set-interval
+              (let
-                (fn () (execute-request el nil nil))
+                ((interval-id nil))
-                (get mods "interval"))
+                (set!
+                  interval-id
+                  (set-interval
+                    (fn
+                      ()
+                      (if
+                        (host-get el "isConnected")
+                        (execute-request el nil nil)
+                        (do
+                          (clear-interval interval-id)
+                          (log-info "poll stopped: element removed"))))
+                    (get mods "interval"))))
               (= kind "intersect")
               (observe-intersection
                 el

web/orchestration.sx

@@ -410,9 +410,20 @@
               (mods (get trigger "modifiers")))
             (cond
               (= kind "poll")
-              (set-interval
+              (let
-                (fn () (execute-request el nil nil))
+                ((interval-id nil))
-                (get mods "interval"))
+                (set!
+                  interval-id
+                  (set-interval
+                    (fn
+                      ()
+                      (if
+                        (host-get el "isConnected")
+                        (execute-request el nil nil)
+                        (do
+                          (clear-interval interval-id)
+                          (log-info "poll stopped: element removed"))))
+                    (get mods "interval"))))
               (= kind "intersect")
               (observe-intersection
                 el