SX docs: configurable shell, SX-native event handlers, nav fixes

- Configurable page shell (~sx-page-shell kwargs + SX_SHELL app config)
  so each app controls its own assets — sx docs loads only sx-browser.js
- SX-evaluated sx-on:* handlers (eval-expr instead of new Function)
  with DOM primitives registered in PRIMITIVES table
- data-init boot mode for pure SX initialization scripts
- Jiggle animation on links while fetching
- Nav: 3-column grid for centered alignment, is-leaf sizing,
  fix map-indexed param order (index, item), guard mod-by-zero
- Async route eval failure now falls back to server fetch
  instead of silently rendering nothing
- Remove duplicate h1 title from ~doc-page
- Re-bootstrap sx-ref.js + sx-browser.js

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shared/sx/ref/js.sx

@@ -347,6 +347,8 @@
   "promise-delayed" "promiseDelayed"
   "abort-previous" "abortPrevious"
   "track-controller" "trackController"
+  "abort-previous-target" "abortPreviousTarget"
+  "track-controller-target" "trackControllerTarget"
   "new-abort-controller" "newAbortController"
   "controller-signal" "controllerSignal"
   "abort-error?" "isAbortError"
@@ -397,7 +399,6 @@
   "try-async-eval-content" "tryAsyncEvalContent"
   "register-io-deps" "registerIoDeps"
   "url-pathname" "urlPathname"
-  "bind-inline-handler" "bindInlineHandler"
   "bind-preload" "bindPreload"
   "mark-processed!" "markProcessed"
   "is-processed?" "isProcessed"
@@ -507,6 +508,7 @@
   "scan-io-refs-walk" "scanIoRefsWalk"
   "transitive-io-refs" "transitiveIoRefs"
   "compute-all-io-refs" "computeAllIoRefs"
+  "component-io-refs-cached" "componentIoRefsCached"
   "component-pure?" "componentPure_p"
   "render-target" "renderTarget"
   "page-render-plan" "pageRenderPlan"