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/sx-urls.sx

@@ -133,7 +133,7 @@
           ;; Geography + Applications + Etc
           (div
             (p :class "font-semibold text-stone-700 text-sm mt-2 mb-1" "Geography")
-            (p (a :href "/sx/(geography.(reactive.demo))" :class "font-mono text-violet-600 hover:underline text-xs" "/(geography.(reactive.demo))"))
+            (p (a :href "/sx/(geography.(reactive.(examples.counter)))" :class "font-mono text-violet-600 hover:underline text-xs" "/(geography.(reactive.(examples.counter)))"))
             (p (a :href "/sx/(geography.(hypermedia.(reference.attributes)))" :class "font-mono text-violet-600 hover:underline text-xs" "/(geography.(hypermedia.(reference.attributes)))"))
             (p (a :href "/sx/(geography.(hypermedia.(example.click-to-load)))" :class "font-mono text-violet-600 hover:underline text-xs" "/(geography.(hypermedia.(example.click-to-load)))"))
             (p (a :href "/sx/(geography.(hypermedia.(example.infinite-scroll)))" :class "font-mono text-violet-600 hover:underline text-xs" "/(geography.(hypermedia.(example.infinite-scroll)))"))
@@ -314,7 +314,7 @@
         (p "Each additional dot pops one more level of nesting. "
            "N dots = pop N-1 levels:")
         (~docs/code :code (highlight
-          ";; Current: /(geography.(hypermedia.(example.progress-bar)))\n;;\n;; ...           → /(geography.(hypermedia))       ;; pop 2 levels\n;; ....          → /(geography)                    ;; pop 3 levels\n;; .....         → /                               ;; pop 4 levels (root)\n;;\n;; Combine with a slug to navigate across sections:\n;; ...reactive.demo  → /(geography.(reactive.demo))  ;; pop 2, into reactive\n;; ....language.(doc.intro)\n;;   → /(language.(doc.intro))                       ;; pop 3, into language"
+          ";; Current: /(geography.(hypermedia.(example.progress-bar)))\n;;\n;; ...           → /(geography.(hypermedia))       ;; pop 2 levels\n;; ....          → /(geography)                    ;; pop 3 levels\n;; .....         → /                               ;; pop 4 levels (root)\n;;\n;; Combine with a slug to navigate across sections:\n;; ...reactive.(examples)  → /(geography.(reactive.(examples)))  ;; pop 2, into reactive\n;; ....language.(doc.intro)\n;;   → /(language.(doc.intro))                       ;; pop 3, into language"
           "lisp")))
 
       (~docs/subsection :title "Why this is functional, not textual"