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/home-stepper.sx

@@ -195,30 +195,30 @@
           ;; Validate — reset to default if out of range
           (when (or (< (deref step-idx) 0) (> (deref step-idx) 16))
             (reset! step-idx 9))))
-      ;; Auto-parse via effect
-      (effect (fn ()
-        (let ((parsed (sx-parse source)))
-          (when (not (empty? parsed))
-            (let ((result (list))
-                  (step-ref (dict "v" 0)))
-              (split-tag (first parsed) result)
-              (reset! steps result)
-              (let ((tokens (list)))
-                (dict-set! step-ref "v" 0)
-                (build-code-tokens (first parsed) tokens step-ref 0)
-                (reset! code-tokens tokens))
-              ;; Defer code DOM build until lake exists
-              (schedule-idle (fn ()
-                (build-code-dom)
-                ;; Clear preview and replay to initial step-idx
-                (let ((preview (get-preview)))
-                  (when preview (dom-set-prop preview "innerHTML" "")))
-                (let ((target (deref step-idx)))
-                  (reset! step-idx 0)
-                  (set-stack (list (get-preview)))
-                  (for-each (fn (_) (do-step)) (slice (deref steps) 0 target)))
-                (update-code-highlight)
-                (run-post-render-hooks))))))))
+      ;; Auto-parse via effect (bind to _ to suppress return value in DOM)
+      (let ((_eff (effect (fn ()
+              (let ((parsed (sx-parse source)))
+                (when (not (empty? parsed))
+                  (let ((result (list))
+                        (step-ref (dict "v" 0)))
+                    (split-tag (first parsed) result)
+                    (reset! steps result)
+                    (let ((tokens (list)))
+                      (dict-set! step-ref "v" 0)
+                      (build-code-tokens (first parsed) tokens step-ref 0)
+                      (reset! code-tokens tokens))
+                    ;; Defer code DOM build until lake exists
+                    (schedule-idle (fn ()
+                      (build-code-dom)
+                      ;; Clear preview and replay to initial step-idx
+                      (let ((preview (get-preview)))
+                        (when preview (dom-set-prop preview "innerHTML" "")))
+                      (let ((target (deref step-idx)))
+                        (reset! step-idx 0)
+                        (set-stack (list (get-preview)))
+                        (for-each (fn (_) (do-step)) (slice (deref steps) 0 target)))
+                      (update-code-highlight)
+                      (run-post-render-hooks))))))))))
       (div :class "space-y-4"
         ;; Code view lake — spans built imperatively, classes updated on step
         (div (~cssx/tw :tokens "font-mono bg-stone-50 rounded p-2 overflow-x-auto leading-relaxed whitespace-pre-wrap")
@@ -241,4 +241,4 @@
                        "text-violet-300 cursor-not-allowed"))
             "\u25b6"))
         ;; Live preview lake
-        (lake :id "home-preview")))))
+        (lake :id "home-preview"))))))