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/progress-status.sx

@@ -0,0 +1,24 @@
+(defcomp
+  (&key percent job-id)
+  (div
+    (~tw :tokens "space-y-3")
+    (div
+      (~tw :tokens "w-full bg-stone-200 rounded-full h-4")
+      (div
+        (~tw :tokens "bg-violet-600 h-4 rounded-full transition-all")
+        :style (str "width: " percent "%")))
+    (p (~tw :tokens "text-sm text-stone-500 text-center") (str percent "% complete"))
+    (when
+      (< percent 100)
+      (div
+        :sx-get (str
+          "/sx/(geography.(hypermedia.(example.(api.progress-status))))?job="
+          job-id)
+        :sx-trigger "load delay:500ms"
+        :sx-target "#progress-target"
+        :sx-swap "innerHTML"))
+    (when
+      (= percent 100)
+      (p
+        (~tw :tokens "text-sm text-emerald-600 font-medium text-center")
+        "Job complete!"))))