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/sxc/handlers/reference.sx

@@ -7,7 +7,7 @@
 ;; ---------------------------------------------------------------------------
 
 (defhandler ref-time (&key)
-  (let ((now (format-time (now) "%H:%M:%S")))
+  (let ((now (helper "now" "%H:%M:%S")))
     (span :class "text-stone-800 text-sm"
       "Server time: " (strong now))))
 
@@ -49,7 +49,7 @@
 ;; ---------------------------------------------------------------------------
 
 (defhandler ref-trigger-search (&key)
-  (let ((q (or (request-arg "q") "")))
+  (let ((q (helper "request-arg" "q" "")))
     (if (empty? q)
       (span :class "text-stone-400 text-sm" "Start typing to trigger a search.")
       (span :class "text-stone-800 text-sm"
@@ -60,7 +60,7 @@
 ;; ---------------------------------------------------------------------------
 
 (defhandler ref-swap-item (&key)
-  (let ((now (format-time (now) "%H:%M:%S")))
+  (let ((now (helper "now" "%H:%M:%S")))
     (div :class "text-sm text-violet-700"
       "New item (" now ")")))
 
@@ -69,7 +69,7 @@
 ;; ---------------------------------------------------------------------------
 
 (defhandler ref-oob (&key)
-  (let ((now (format-time (now) "%H:%M:%S")))
+  (let ((now (helper "now" "%H:%M:%S")))
     (<>
       (span :class "text-emerald-700 text-sm"
         "Main updated at " now)
@@ -82,7 +82,7 @@
 ;; ---------------------------------------------------------------------------
 
 (defhandler ref-select-page (&key)
-  (let ((now (format-time (now) "%H:%M:%S")))
+  (let ((now (helper "now" "%H:%M:%S")))
     (<>
       (div :id "the-header"
         (h3 "Page header — not selected"))
@@ -98,7 +98,7 @@
 
 (defhandler ref-slow-echo (&key)
   (sleep 800)
-  (let ((q (or (request-arg "q") "")))
+  (let ((q (helper "request-arg" "q" "")))
     (span :class "text-stone-800 text-sm"
       "Echo: " (strong q))))
 
@@ -116,7 +116,7 @@
 ;; ---------------------------------------------------------------------------
 
 (defhandler ref-echo-headers (&key)
-  (let ((headers (request-headers :prefix "X-")))
+  (let ((headers (helper "request-headers" :prefix "X-")))
     (if (empty? headers)
       (span :class "text-stone-400 text-sm" "No custom headers received.")
       (ul :class "text-sm text-stone-700 space-y-1"
@@ -129,7 +129,7 @@
 ;; ---------------------------------------------------------------------------
 
 (defhandler ref-echo-vals (&key)
-  (let ((vals (request-args)))
+  (let ((vals (helper "request-args")))
     (if (empty? vals)
       (span :class "text-stone-400 text-sm" "No values received.")
       (ul :class "text-sm text-stone-700 space-y-1"