SPA navigation, page component refactors, WASM rebuild

Refactor page components (docs, examples, specs, reference, layouts)
and adapters (adapter-sx, boot-helpers, orchestration) across sx/ and
web/ directories. Add Playwright SPA navigation tests. Rebuild WASM
kernel with updated bytecode. Add OCaml primitives for request handling.

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

sx/sxc/docs.sx

@@ -74,8 +74,8 @@
         (a
           :href href
           :sx-get href
-          :sx-target "#main-panel"
-          :sx-select "#main-panel"
+          :sx-target "#sx-content"
+          :sx-select "#sx-content"
           :sx-swap "outerHTML"
           :sx-push-url "true"
           :class "text-violet-700 hover:text-violet-900 underline"
@@ -116,8 +116,8 @@
         (a
           :href (nth item 1)
           :sx-get (nth item 1)
-          :sx-target "#main-panel"
-          :sx-select "#main-panel"
+          :sx-target "#sx-content"
+          :sx-select "#sx-content"
           :sx-swap "outerHTML"
           :sx-push-url "true"
           :class (str