Add event bindings and data-sx-emit processing

- adapter-dom.sx: detect :on-click/:on-submit etc. in render-dom-element
  — if attr starts with "on-" and value is callable, wire via dom-listen
- orchestration.sx: add process-emit-elements for data-sx-emit attrs
  — auto-dispatch custom events on click with optional JSON detail
- bootstrap_js.py: add processEmitElements RENAME
- Regenerate sx-ref.js with all changes
- Update reactive-islands status table

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shared/sx/ref/adapter-dom.sx

@@ -170,6 +170,12 @@
                     ;; nil or false → skip
                     (or (nil? attr-val) (= attr-val false))
                       nil
+                    ;; Event handler: on-click, on-submit, on-input, etc.
+                    ;; Value must be callable (lambda/function)
+                    (and (starts-with? attr-name "on-")
+                         (callable? attr-val))
+                      (let ((event-name (substring attr-name 3 (string-length attr-name))))
+                        (dom-listen el event-name attr-val))
                     ;; Boolean attr
                     (contains? BOOLEAN_ATTRS attr-name)
                       (when attr-val (dom-set-attr el attr-name ""))
@@ -589,6 +595,11 @@
 ;;   (dom-child-nodes frag)       → list of child nodes
 ;;   (dom-remove-children-after m)→ void (remove all siblings after marker)
 ;;   (dom-set-data el key val)    → void (store arbitrary data on element)
+;;   (dom-get-data el key)        → any (retrieve data stored on element)
+;;
+;; Event handling:
+;;   (dom-listen el name handler) → remove-fn (addEventListener, returns remover)
+;;   (dom-dispatch el name detail)→ boolean (dispatch CustomEvent, bubbles: true)
 ;;
 ;; Content parsing:
 ;;   (dom-parse-html s)           → DocumentFragment from HTML string

shared/sx/ref/bootstrap_js.py

@@ -397,6 +397,7 @@ class JSEmitter:
             "bind-sse": "bindSse",
             "bind-sse-swap": "bindSseSwap",
             "bind-inline-handlers": "bindInlineHandlers",
+            "process-emit-elements": "processEmitElements",
             "bind-preload-for": "bindPreloadFor",
             "do-preload": "doPreload",
             "VERB_SELECTOR": "VERB_SELECTOR",

shared/sx/ref/orchestration.sx

@@ -1087,10 +1087,11 @@
             (mark-processed! el "verb")
             (process-one el)))
         els))
-    ;; Also process boost, SSE, inline handlers
+    ;; Also process boost, SSE, inline handlers, emit attributes
     (process-boosted root)
     (process-sse root)
-    (bind-inline-handlers root)))
+    (bind-inline-handlers root)
+    (process-emit-elements root)))
 
 
 (define process-one
@@ -1104,6 +1105,40 @@
           (bind-preload-for el))))))
 
 
+;; --------------------------------------------------------------------------
+;; data-sx-emit — auto-dispatch custom events for lake→island bridge
+;; --------------------------------------------------------------------------
+;;
+;; Elements with data-sx-emit="event-name" get a click listener that
+;; dispatches a CustomEvent with that name. Optional data-sx-emit-detail
+;; provides JSON payload.
+;;
+;; Example:
+;;   <button data-sx-emit="cart:add"
+;;           data-sx-emit-detail='{"id":42,"name":"Widget"}'>
+;;     Add to Cart
+;;   </button>
+;;
+;; On click → dispatches CustomEvent "cart:add" with detail {id:42, name:"Widget"}
+;; The event bubbles up to the island container where bridge-event catches it.
+
+(define process-emit-elements
+  (fn (root)
+    (let ((els (dom-query-all (or root (dom-body)) "[data-sx-emit]")))
+      (for-each
+        (fn (el)
+          (when (not (is-processed? el "emit"))
+            (mark-processed! el "emit")
+            (let ((event-name (dom-get-attr el "data-sx-emit")))
+              (when event-name
+                (dom-listen el "click"
+                  (fn (e)
+                    (let ((detail-json (dom-get-attr el "data-sx-emit-detail"))
+                          (detail (if detail-json (json-parse detail-json) (dict))))
+                      (dom-dispatch el event-name detail))))))))
+        els))))
+
+
 ;; --------------------------------------------------------------------------
 ;; History: popstate handler
 ;; --------------------------------------------------------------------------