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/sx/nav-data.sx

@@ -9,7 +9,6 @@
   (dict :label "Evaluator" :href "/docs/evaluator")
   (dict :label "Primitives" :href "/docs/primitives")
   (dict :label "Special Forms" :href "/docs/special-forms")
-  (dict :label "CSS" :href "/docs/css")
   (dict :label "Server Rendering" :href "/docs/server-rendering")))
 
 (define reference-nav-items (list
@@ -58,6 +57,7 @@
 (define cssx-nav-items (list
   (dict :label "Overview" :href "/cssx/")
   (dict :label "Patterns" :href "/cssx/patterns")
+  (dict :label "Delivery" :href "/cssx/delivery")
   (dict :label "Async CSS" :href "/cssx/async")
   (dict :label "Live Styles" :href "/cssx/live")
   (dict :label "Comparisons" :href "/cssx/comparisons")
@@ -153,8 +153,6 @@
         :summary "OAuth-based sharing to Facebook, Instagram, Threads, Twitter/X, LinkedIn, and Mastodon.")
   (dict :label "SX CI Pipeline" :href "/plans/sx-ci"
         :summary "Build, test, and deploy in s-expressions — CI pipelines as SX components.")
-  (dict :label "CSSX Components" :href "/plans/cssx-components"
-        :summary "Done — see /cssx/. Styling as components: style dictionary removed, defcomps handle all styling.")
   (dict :label "Live Streaming" :href "/plans/live-streaming"
         :summary "SSE and WebSocket transports for re-resolving suspense slots after initial page load — live data, real-time collaboration.")))