Replace env free-variable threading with IO-primitive auto-fetch macros

Layout components now self-resolve context (cart-mini, auth-menu, nav-tree,
rights, URLs) via new IO primitives (root-header-ctx, select-colours,
account-nav-ctx, app-rights) and defmacro wrappers (~root-header-auto,
~auth-header-row-auto, ~root-mobile-auto). This eliminates _ctx_to_env(),
HELPER_CSS_CLASSES, and verbose :key threading across all 10 services.

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

blog/sx/admin.sx

@@ -170,6 +170,15 @@
     (summary :class "cursor-pointer px-4 py-3 font-medium text-sm bg-stone-100 hover:bg-stone-200 select-none" title)
     (div :class "p-4 overflow-x-auto text-xs" content)))
 
+(defcomp ~blog-preview-rendered (&key html)
+  (div :class "blog-content prose max-w-none" (raw! html)))
+
+(defcomp ~blog-preview-empty ()
+  (div :class "p-8 text-stone-500" "No content to preview."))
+
+(defcomp ~blog-admin-placeholder ()
+  (div :class "pb-8"))
+
 ;; ---------------------------------------------------------------------------
 ;; Data-driven content defcomps (called from defpages with service data)
 ;; ---------------------------------------------------------------------------

blog/sx/layouts.sx

@@ -1,37 +1,38 @@
-;; Blog layout defcomps — root header from env free variables,
-;; blog-specific headers passed as &key params.
+;; Blog layout defcomps — fully self-contained via IO primitives.
 
-;; --- Blog layout (root + invisible blog header) ---
+;; --- Blog header (invisible row for blog-header-child swap target) ---
 
-(defcomp ~blog-layout-full (&key blog-header)
-  (<> (~root-header :cart-mini cart-mini :blog-url blog-url :site-title site-title
-                     :app-label app-label :nav-tree nav-tree :auth-menu auth-menu
-                     :nav-panel nav-panel :settings-url settings-url :is-admin is-admin)
-    blog-header))
+(defcomp ~blog-header (&key oob)
+  (~menu-row-sx :id "blog-row" :level 1
+    :link-label-content (div)
+    :child-id "blog-header-child" :oob oob))
+
+;; --- Blog layout (root + blog header) ---
+
+(defcomp ~blog-layout-full ()
+  (<> (~root-header-auto)
+    (~blog-header)))
 
 ;; --- Settings layout (root + settings header) ---
 
 (defcomp ~settings-layout-full (&key settings-header)
-  (<> (~root-header :cart-mini cart-mini :blog-url blog-url :site-title site-title
-                     :app-label app-label :nav-tree nav-tree :auth-menu auth-menu
-                     :nav-panel nav-panel :settings-url settings-url :is-admin is-admin)
+  (<> (~root-header-auto)
     settings-header))
 
 ;; --- Sub-settings layout (root + settings + sub row) ---
 
 (defcomp ~sub-settings-layout-full (&key settings-header sub-header)
-  (<> (~root-header :cart-mini cart-mini :blog-url blog-url :site-title site-title
-                     :app-label app-label :nav-tree nav-tree :auth-menu auth-menu
-                     :nav-panel nav-panel :settings-url settings-url :is-admin is-admin)
+  (<> (~root-header-auto)
     settings-header sub-header))
 
 (defcomp ~sub-settings-layout-oob (&key settings-header-oob sub-header-oob)
   (<> settings-header-oob sub-header-oob))
 
-;; --- Settings nav links (replaces Python _settings_nav_sx loop) ---
+;; --- Settings nav links — uses (select-colours) IO primitive ---
 
-(defcomp ~blog-settings-nav (&key select-colours)
-  (let* ((links (list
+(defcomp ~blog-settings-nav ()
+  (let* ((sc (select-colours))
+         (links (list
            (dict :endpoint "menu_items.defpage_menu_items_page" :icon "fa fa-bars" :label "Menu Items")
            (dict :endpoint "snippets.defpage_snippets_page" :icon "fa fa-puzzle-piece" :label "Snippets")
            (dict :endpoint "blog.tag_groups_admin.defpage_tag_groups_page" :icon "fa fa-tags" :label "Tag Groups")
@@ -41,7 +42,7 @@
         :href (url-for (get lnk "endpoint"))
         :icon (get lnk "icon")
         :label (get lnk "label")
-        :select-colours (or select-colours "")))
+        :select-colours (or sc "")))
       links))))
 
 ;; --- Editor panel wrapper ---