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-put-demo.sx

@@ -0,0 +1,14 @@
+(defcomp
+  ()
+  (div
+    :id "ref-put-view"
+    (div
+      (~tw :tokens "flex items-center justify-between p-3 bg-stone-100 rounded")
+      (span (~tw :tokens "text-stone-700 text-sm") "Status: " (strong "draft"))
+      (button
+        :sx-put "/sx/(geography.(hypermedia.(reference.(api.status))))"
+        :sx-target "#ref-put-view"
+        :sx-swap "innerHTML"
+        :sx-vals "{\"status\": \"published\"}"
+        (~tw :tokens "px-3 py-1 bg-violet-600 text-white rounded text-sm hover:bg-violet-700")
+        "Publish"))))