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-disable-demo.sx

@@ -0,0 +1,30 @@
+(defcomp
+  ()
+  (div
+    (~tw :tokens "space-y-3")
+    (div
+      (~tw :tokens "grid grid-cols-2 gap-3")
+      (div
+        (~tw :tokens "p-3 border border-stone-200 rounded")
+        (p (~tw :tokens "text-xs text-stone-400 mb-2") "sx enabled")
+        (button
+          :sx-get "/sx/(geography.(hypermedia.(reference.(api.time))))"
+          :sx-target "#ref-dis-a"
+          :sx-swap "innerHTML"
+          (~tw :tokens "px-3 py-1 bg-violet-600 text-white rounded text-sm")
+          "Load")
+        (div :id "ref-dis-a" (~tw :tokens "mt-2 text-sm text-stone-500") "—"))
+      (div
+        :sx-disable "true"
+        (~tw :tokens "p-3 border border-stone-200 rounded")
+        (p (~tw :tokens "text-xs text-stone-400 mb-2") "sx disabled")
+        (button
+          :sx-get "/sx/(geography.(hypermedia.(reference.(api.time))))"
+          :sx-target "#ref-dis-b"
+          :sx-swap "innerHTML"
+          (~tw :tokens "px-3 py-1 bg-stone-400 text-white rounded text-sm")
+          "Load")
+        (div
+          :id "ref-dis-b"
+          (~tw :tokens "mt-2 text-sm text-stone-500")
+          "Button won't fire sx request")))))