Fix reactive islands client-side navigation and hydration

Three bugs prevented islands from working during SX wire navigation:

1. components_for_request() only bundled Component and Macro defs, not
   Island defs — client never received defisland definitions during
   navigation (components_for_page for initial HTML shell was correct).

2. hydrate-island used morph-children which can't transfer addEventListener
   event handlers from freshly rendered DOM to existing nodes. Changed to
   clear+append so reactive DOM with live signal subscriptions is inserted
   directly.

3. asyncRenderToDom (client-side async page eval) checked _component but
   not _island on ~-prefixed names — islands fell through to generic eval
   which failed. Now delegates to renderDomIsland.

4. setInterval_/setTimeout_ passed SX Lambda objects directly to native
   timers. JS coerced them to "[object Object]" and tried to eval as code,
   causing "missing ] after element list". Added _wrapSxFn to convert SX
   lambdas to JS functions before passing to timers.

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

shared/sx/ref/boot.sx

@@ -361,8 +361,11 @@
                         (fn (disposable) (append! disposers disposable))
                         (fn () (render-to-dom (component-body comp) local nil)))))
 
-                ;; Morph existing DOM against reactive output
-                (morph-children el body-dom)
+                ;; Clear existing content and append reactive DOM directly.
+                ;; Unlike morph-children, this preserves addEventListener-based
+                ;; event handlers on the freshly rendered nodes.
+                (dom-set-text-content el "")
+                (dom-append el body-dom)
 
                 ;; Store disposers for cleanup
                 (dom-set-data el "sx-disposers" disposers)