SXC content: docs/examples/home/reference pages + SX testing runner

New sxc/ content tree with 120 page files across docs, examples, home,
and reference demos. sx/sx/testing/ adds page-runner.sx (317L) and
index-runner.sx (394L) — SX-native test runner pages for
browser-based evaluation.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

sx/sxc/reference/ref-event-client-route-demo.sx

@@ -0,0 +1,26 @@
+(defcomp
+  ()
+  (div
+    (~tw :tokens "space-y-3")
+    (p
+      (~tw :tokens "text-sm text-stone-600")
+      "Open DevTools console, then navigate to a pure page (no :data expression). "
+      "You'll see \"sx:route client /path\" in the console — no network request is made.")
+    (div
+      (~tw :tokens "flex gap-2 flex-wrap")
+      (a
+        :href "/sx/(etc.(essay))"
+        (~tw :tokens "px-3 py-1 bg-violet-100 text-violet-700 rounded text-sm no-underline hover:bg-violet-200")
+        "Essays")
+      (a
+        :href "/sx/(etc.(plan))"
+        (~tw :tokens "px-3 py-1 bg-violet-100 text-violet-700 rounded text-sm no-underline hover:bg-violet-200")
+        "Plans")
+      (a
+        :href "/sx/(applications.(protocol))"
+        (~tw :tokens "px-3 py-1 bg-violet-100 text-violet-700 rounded text-sm no-underline hover:bg-violet-200")
+        "Protocols"))
+    (p
+      (~tw :tokens "text-xs text-stone-400")
+      "The sx:clientRoute event fires on the swap target and bubbles to document.body. "
+      "Apps use it to update nav selection, analytics, or other post-navigation state.")))