Move blog composition from Python to .sx defcomps (Phase 4)

- Settings form: ~135 lines raw HTML → ~blog-settings-form-content defcomp
- Data introspection: ~110 lines raw HTML → ~blog-data-table-content with
  recursive ~blog-data-model-content defcomps, Python extracts ORM data only
- Preview: sx_call composition → ~blog-preview-content defcomp
- Entries browser: ~65 lines raw HTML → ~blog-entries-browser-content +
  ~blog-calendar-browser-item + ~blog-associated-entries-from-data defcomps
- Editor panels: sx_call composition in both helpers.py and renders.py →
  ~blog-editor-content and ~blog-edit-content composition defcomps
- renders.py: 178 → 25 lines (87% reduction)
- routes.py _render_associated_entries: data extraction → single sx_call

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

blog/sx/editor.sx

@@ -303,3 +303,48 @@
 
     ;; Drag over editor
     ".sx-drag-over { outline: 2px dashed #3b82f6; outline-offset: -2px; border-radius: 4px; }"))
+
+;; ---------------------------------------------------------------------------
+;; Editor panel composition — replaces render_editor_panel (new post/page)
+;; ---------------------------------------------------------------------------
+
+(defcomp ~blog-editor-content (&key csrf title-placeholder create-label
+                                     css-href js-src sx-editor-js-src init-js
+                                     save-error)
+  (~blog-editor-panel :parts
+    (<>
+      (when save-error (~blog-editor-error :error save-error))
+      (~blog-editor-form :csrf csrf :title-placeholder title-placeholder
+        :create-label create-label)
+      (~blog-editor-styles :css-href css-href)
+      (~sx-editor-styles)
+      (~blog-editor-scripts :js-src js-src :sx-editor-js-src sx-editor-js-src
+        :init-js init-js))))
+
+;; ---------------------------------------------------------------------------
+;; Edit content composition — replaces _h_post_edit_content (existing post)
+;; ---------------------------------------------------------------------------
+
+(defcomp ~blog-edit-content (&key csrf updated-at title-val excerpt-val
+                                   feature-image feature-image-caption
+                                   sx-content-val lexical-json has-sx
+                                   title-placeholder status already-emailed
+                                   newsletter-options footer-extra
+                                   css-href js-src sx-editor-js-src init-js
+                                   save-error)
+  (~blog-editor-panel :parts
+    (<>
+      (when save-error (~blog-editor-error :error save-error))
+      (~blog-editor-edit-form
+        :csrf csrf :updated-at updated-at
+        :title-val title-val :excerpt-val excerpt-val
+        :feature-image feature-image :feature-image-caption feature-image-caption
+        :sx-content-val sx-content-val :lexical-json lexical-json
+        :has-sx has-sx :title-placeholder title-placeholder
+        :status status :already-emailed already-emailed
+        :newsletter-options newsletter-options :footer-extra footer-extra)
+      (~blog-editor-publish-js :already-emailed already-emailed)
+      (~blog-editor-styles :css-href css-href)
+      (~sx-editor-styles)
+      (~blog-editor-scripts :js-src js-src :sx-editor-js-src sx-editor-js-src
+        :init-js init-js))))