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/sxc/pages/docs.sx

@@ -349,15 +349,22 @@
         "extensions" (~spec-overview-content
           :spec-title "Extensions"
           :spec-files (make-spec-files extension-spec-items))
-        :else (let ((spec (find-spec slug)))
-          (if spec
-            (~spec-detail-content
-              :spec-title (get spec "title")
-              :spec-desc (get spec "desc")
-              :spec-filename (get spec "filename")
-              :spec-source (read-spec-file (get spec "filename"))
-              :spec-prose (get spec "prose"))
-            (~spec-not-found :slug slug)))))))
+        :else (cond
+          (starts-with? slug "explore/")
+            (let ((spec-slug (slice slug 8 (string-length slug)))
+                  (data (spec-explorer-data spec-slug)))
+              (if data
+                (~spec-explorer-content :data data)
+                (~spec-not-found :slug spec-slug)))
+          :else (let ((spec (find-spec slug)))
+            (if spec
+              (~spec-detail-content
+                :spec-title (get spec "title")
+                :spec-desc (get spec "desc")
+                :spec-filename (get spec "filename")
+                :spec-source (read-spec-file (get spec "filename"))
+                :spec-prose (get spec "prose"))
+              (~spec-not-found :slug slug))))))))
 
 ;; ---------------------------------------------------------------------------
 ;; Bootstrappers section