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/edit-row-form.sx

@@ -0,0 +1,44 @@
+(defcomp
+  (&key id name price stock)
+  (tr
+    :id (str "erow-" id)
+    (~tw :tokens "border-b border-stone-100 bg-violet-50")
+    (td
+      (~tw :tokens "px-3 py-2")
+      (input
+        :type "text"
+        :name "name"
+        :value name
+        (~tw :tokens "w-full px-2 py-1 border border-stone-300 rounded text-sm")))
+    (td
+      (~tw :tokens "px-3 py-2")
+      (input
+        :type "text"
+        :name "price"
+        :value price
+        (~tw :tokens "w-20 px-2 py-1 border border-stone-300 rounded text-sm")))
+    (td
+      (~tw :tokens "px-3 py-2")
+      (input
+        :type "text"
+        :name "stock"
+        :value stock
+        (~tw :tokens "w-20 px-2 py-1 border border-stone-300 rounded text-sm")))
+    (td
+      (~tw :tokens "px-3 py-2 space-x-1")
+      (button
+        :sx-post (str "/sx/(geography.(hypermedia.(example.(api.(editrow." id ")))))")
+        :sx-target (str "#erow-" id)
+        :sx-swap "outerHTML"
+        :sx-include (str "#erow-" id)
+        (~tw :tokens "text-sm text-emerald-600 hover:text-emerald-800")
+        "save")
+      (button
+        :sx-get (str
+          "/sx/(geography.(hypermedia.(example.(api.(editrow-cancel."
+          id
+          ")))))")
+        :sx-target (str "#erow-" id)
+        :sx-swap "outerHTML"
+        (~tw :tokens "text-sm text-stone-500 hover:text-stone-700")
+        "cancel"))))