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-boost-demo.sx

@@ -0,0 +1,23 @@
+(defcomp
+  ()
+  (div
+    (~tw :tokens "space-y-3")
+    (nav
+      :sx-boost "true"
+      (~tw :tokens "flex gap-3")
+      (a
+        :href "/sx/(geography.(hypermedia.(reference-detail.attributes.sx-get)))"
+        (~tw :tokens "text-violet-600 hover:text-violet-800 underline text-sm")
+        "sx-get")
+      (a
+        :href "/sx/(geography.(hypermedia.(reference-detail.attributes.sx-post)))"
+        (~tw :tokens "text-violet-600 hover:text-violet-800 underline text-sm")
+        "sx-post")
+      (a
+        :href "/sx/(geography.(hypermedia.(reference-detail.attributes.sx-target)))"
+        (~tw :tokens "text-violet-600 hover:text-violet-800 underline text-sm")
+        "sx-target"))
+    (p
+      (~tw :tokens "text-xs text-stone-400")
+      "These links use AJAX navigation via sx-boost — no sx-get needed on each link. "
+      "#sx-content")))