OCaml evaluator for page dispatch + handler aser, 83/83 Playwright tests

Major architectural change: page function dispatch and handler execution
now go through the OCaml kernel instead of the Python bootstrapped evaluator.

OCaml integration:
- Page dispatch: bridge.eval() evaluates SX URL expressions (geography, marshes, etc.)
- Handler aser: bridge.aser() serializes handler responses as SX wire format
- _ensure_components loads all .sx files into OCaml kernel (spec, web adapter, handlers)
- defhandler/defpage registered as no-op special forms so handler files load
- helper IO primitive dispatches to Python page helpers + IO handlers
- ok-raw response format for SX wire format (no double-escaping)
- Natural list serialization in eval (no (list ...) wrapper)
- Clean pipe: _read_until_ok always sends io-response on error

SX adapter (aser):
- scope-emit!/scope-peek aliases to avoid CEK special form conflict
- aser-fragment/aser-call: strings starting with "(" pass through unserialized
- Registered cond-scheme?, is-else-clause?, primitive?, get-primitive in kernel
- random-int, parse-int as kernel primitives; json-encode, into via IO bridge

Handler migration:
- All IO calls converted to (helper "name" args...) pattern
- request-arg, request-form, state-get, state-set!, now, component-source etc.
- Fixed bare (effect ...) in island bodies leaking disposer functions as text
- Fixed lower-case → lower, ~search-results → ~examples/search-results

Reactive islands:
- sx-hydrate-islands called after client-side navigation swap
- force-dispose-islands-in for outerHTML swaps (clears hydration markers)
- clear-processed! platform primitive for re-hydration

Content restructuring:
- Design, event bridge, named stores, phase 2 consolidated into reactive overview
- Marshes split into overview + 5 example sub-pages
- Nav links use sx-get/sx-target for client-side navigation

Playwright test suite (sx/tests/test_demos.py):
- 83 tests covering hypermedia demos, reactive islands, marshes, spec explorer
- Server-side rendering, handler interactions, island hydration, navigation

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

sx/sx/geography/cek.sx

@@ -58,18 +58,18 @@
   (let ((running (signal false))
         (elapsed (signal 0))
         (time-text (create-text-node "0.0s"))
-        (btn-text (create-text-node "Start")))
-    (effect (fn ()
-      (when (deref running)
-        (let ((id (set-interval (fn () (swap! elapsed inc)) 100)))
-          (fn () (clear-interval id))))))
-    (effect (fn ()
-      (let ((e (deref elapsed)))
-        (dom-set-text-content time-text
-          (str (floor (/ e 10)) "." (mod e 10) "s")))))
-    (effect (fn ()
-      (dom-set-text-content btn-text
-        (if (deref running) "Stop" "Start"))))
+        (btn-text (create-text-node "Start"))
+        (_e1 (effect (fn ()
+               (when (deref running)
+                 (let ((id (set-interval (fn () (swap! elapsed inc)) 100)))
+                   (fn () (clear-interval id)))))))
+        (_e2 (effect (fn ()
+               (let ((e (deref elapsed)))
+                 (dom-set-text-content time-text
+                   (str (floor (/ e 10)) "." (mod e 10) "s"))))))
+        (_e3 (effect (fn ()
+               (dom-set-text-content btn-text
+                 (if (deref running) "Stop" "Start"))))))
     (div :class "rounded-lg border border-stone-200 p-4"
       (div :class "flex items-center gap-3"
         (span :class "text-2xl font-bold text-violet-700 font-mono min-w-[5ch]" time-text)
@@ -82,10 +82,10 @@
 (defisland ~geography/cek/demo-batch ()
   (let ((first-sig  (signal 0))
         (second-sig (signal 0))
-        (renders    (signal 0)))
-    (effect (fn ()
-      (deref first-sig) (deref second-sig)
-      (swap! renders inc)))
+        (renders    (signal 0))
+        (_eff (effect (fn ()
+                (deref first-sig) (deref second-sig)
+                (swap! renders inc)))))
     (div :class "rounded-lg border border-stone-200 p-4 space-y-2"
       (div :class "flex items-center gap-4 text-sm"
         (span (str "first: " (deref first-sig)))