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/examples/poll-result.sx

@@ -0,0 +1,17 @@
+(defcomp
+  (&key time count)
+  (div
+    (p (~tw :tokens "text-stone-800 font-medium") (str "Server time: " time))
+    (p (~tw :tokens "text-stone-500 text-sm mt-1") (str "Poll count: " count))
+    (div
+      (~tw :tokens "mt-2 flex justify-center")
+      (div
+        (~tw :tokens "flex gap-1")
+        (map
+          (fn
+            (i)
+            (div
+              :class (str
+                "w-2 h-2 rounded-full "
+                (if (<= i count) "bg-violet-500" "bg-stone-200"))))
+          (list 1 2 3 4 5 6 7 8 9 10))))))