modular editor: extract original scripts into _page_editor_scripts.html

Now 3 shared modules (zero code duplication):
- _page_editor_content.html — editor HTML (title block, slash menu, toolbar etc)
- _page_editor_scripts.html — 100% original editorState() JS (CMDS, render,
  save, slash, database, share/publish, favorites, formatting, etc)
- Used by page_editor.html (full page) and page_editor_embed.html (peek iframe)

Embed page_editor_embed.html now has the exact same editor as full page.
One change to _page_editor_scripts.html updates both views.

app/templates/_page_editor_content.html

@@ -510,4 +510,4 @@
         ></span>
         <span class="statusbar-right" x-text="blocks.length+' blocks'"></span>
     </div>
-</div>
+</div>