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-patch-demo.sx

@@ -0,0 +1,27 @@
+(defcomp
+  ()
+  (div
+    :id "ref-patch-view"
+    (~tw :tokens "space-y-2")
+    (div
+      (~tw :tokens "p-3 bg-stone-100 rounded")
+      (span
+        (~tw :tokens "text-stone-700 text-sm")
+        "Theme: "
+        (strong :id "ref-patch-val" "light")))
+    (div
+      (~tw :tokens "flex gap-2")
+      (button
+        :sx-patch "/sx/(geography.(hypermedia.(reference.(api.theme))))"
+        :sx-vals "{\"theme\": \"dark\"}"
+        :sx-target "#ref-patch-val"
+        :sx-swap "innerHTML"
+        (~tw :tokens "px-3 py-1 bg-stone-800 text-white rounded text-sm")
+        "Dark")
+      (button
+        :sx-patch "/sx/(geography.(hypermedia.(reference.(api.theme))))"
+        :sx-vals "{\"theme\": \"light\"}"
+        :sx-target "#ref-patch-val"
+        :sx-swap "innerHTML"
+        (~tw :tokens "px-3 py-1 bg-stone-100 border border-stone-300 text-stone-700 rounded text-sm")
+        "Light"))))