Add spec explorer: structured interactive view of SX spec files

- _spec_explorer_data() helper: parses spec files into sections, defines,
  effects, params, source blocks, and Python translations via PyEmitter
- specs-explorer.sx: 10 defcomp components for explorer UI — cards with
  effect badges, typed param lists, collapsible SX/Python translation panels
- Route at /language/specs/explore/<slug> via docs.sx
- "Explore" link on existing spec detail pages

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

sx/sx/specs.sx

@@ -334,9 +334,15 @@ deps.sx             depends on: eval")))
 
 (defcomp ~spec-detail-content (&key (spec-title :as string) (spec-desc :as string) (spec-filename :as string) (spec-source :as string) (spec-prose :as string?))
   (~doc-page :title spec-title
-    (div :class "flex items-baseline gap-3 mb-4"
+    (div :class "flex items-center gap-3 mb-4"
       (span :class "text-sm text-stone-400 font-mono" spec-filename)
-      (span :class "text-sm text-stone-500" spec-desc))
+      (span :class "text-sm text-stone-500 flex-1" spec-desc)
+      (a :href (str "/language/specs/explore/" (replace spec-filename ".sx" ""))
+         :sx-get (str "/language/specs/explore/" (replace spec-filename ".sx" ""))
+         :sx-target "#main-panel" :sx-select "#main-panel"
+         :sx-swap "outerHTML" :sx-push-url "true"
+         :class "text-sm text-violet-600 hover:text-violet-800 font-medium whitespace-nowrap"
+        "Explore"))
     (when spec-prose
       (div :class "mb-6 space-y-3"
         (p :class "text-stone-600 leading-relaxed" spec-prose)