Consolidate CSSX docs: add delivery page, remove old CSS docs and plan

Moved on-demand CSS delivery protocol from docs/css into /cssx/delivery,
framed as one strategy among several. Removed the CSSX Components plan
(now redundant with the top-level /cssx/ section).

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

sx/sxc/pages/docs.sx

@@ -46,7 +46,6 @@
                    :prims (~doc-primitives-tables :primitives (primitives-data)))
     "special-forms" (~docs-special-forms-content
                       :forms (~doc-special-forms-tables :forms (special-forms-data)))
-    "css" (~docs-css-content)
     "server-rendering" (~docs-server-rendering-content)
     :else (~docs-introduction-content)))
 
@@ -313,6 +312,7 @@
     :selected (or (find-current cssx-nav-items slug) ""))
   :content (case slug
     "patterns" (~cssx-patterns-content)
+    "delivery" (~cssx-delivery-content)
     "async" (~cssx-async-content)
     "live" (~cssx-live-content)
     "comparisons" (~cssx-comparison-content)
@@ -567,7 +567,6 @@
     "glue-decoupling" (~plan-glue-decoupling-content)
     "social-sharing" (~plan-social-sharing-content)
     "sx-ci" (~plan-sx-ci-content)
-    "cssx-components" (~plan-cssx-components-content)
     "live-streaming" (~plan-live-streaming-content)
     :else (~plans-index-content)))