Remove render_to_sx from public API: enforce sx_call for all service code

Replace ~250 render_to_sx calls across all services with sync sx_call,
converting many async functions to sync where no other awaits remained.
Make render_to_sx/render_to_sx_with_env private (_render_to_sx).
Add (post-header-ctx) IO primitive and shared post/post-admin defmacros.
Convert built-in post/post-admin layouts from Python to register_sx_layout
with .sx defcomps. Remove dead post_admin_mobile_nav_sx.

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

blog/sxc/pages/helpers.py

@@ -126,22 +126,22 @@ def _register_blog_helpers() -> None:
 
 # --- Editor helpers ---
 
-async def _h_editor_content(**kw):
+def _h_editor_content(**kw):
     from .renders import render_editor_panel
-    return await render_editor_panel()
+    return render_editor_panel()
 
 
-async def _h_editor_page_content(**kw):
+def _h_editor_page_content(**kw):
     from .renders import render_editor_panel
-    return await render_editor_panel(is_page=True)
+    return render_editor_panel(is_page=True)
 
 
 # --- Post admin helpers ---
 
 async def _h_post_admin_content(slug=None, **kw):
     await _ensure_post_data(slug)
-    from shared.sx.helpers import render_to_sx
-    return await render_to_sx("blog-admin-placeholder")
+    from shared.sx.helpers import sx_call
+    return sx_call("blog-admin-placeholder")
 
 
 async def _h_post_data_content(slug=None, **kw):
@@ -264,32 +264,32 @@ async def _h_post_preview_content(slug=None, **kw):
     await _ensure_post_data(slug)
     from quart import g
     from shared.services.registry import services
-    from shared.sx.helpers import render_to_sx
+    from shared.sx.helpers import sx_call
     from shared.sx.parser import SxExpr
 
     preview = await services.blog_page.preview_data(g.s)
 
     sections: list[str] = []
     if preview.get("sx_pretty"):
-        sections.append(await render_to_sx("blog-preview-section",
+        sections.append(sx_call("blog-preview-section",
             title="S-Expression Source", content=SxExpr(preview["sx_pretty"])))
     if preview.get("json_pretty"):
-        sections.append(await render_to_sx("blog-preview-section",
+        sections.append(sx_call("blog-preview-section",
             title="Lexical JSON", content=SxExpr(preview["json_pretty"])))
     if preview.get("sx_rendered"):
-        rendered_sx = await render_to_sx("blog-preview-rendered", html=preview["sx_rendered"])
-        sections.append(await render_to_sx("blog-preview-section",
+        rendered_sx = sx_call("blog-preview-rendered", html=preview["sx_rendered"])
+        sections.append(sx_call("blog-preview-section",
             title="SX Rendered", content=SxExpr(rendered_sx)))
     if preview.get("lex_rendered"):
-        rendered_sx = await render_to_sx("blog-preview-rendered", html=preview["lex_rendered"])
-        sections.append(await render_to_sx("blog-preview-section",
+        rendered_sx = sx_call("blog-preview-rendered", html=preview["lex_rendered"])
+        sections.append(sx_call("blog-preview-section",
             title="Lexical Rendered", content=SxExpr(rendered_sx)))
 
     if not sections:
-        return await render_to_sx("blog-preview-empty")
+        return sx_call("blog-preview-empty")
 
     inner = " ".join(sections)
-    return await render_to_sx("blog-preview-panel", sections=SxExpr(f"(<> {inner})"))
+    return sx_call("blog-preview-panel", sections=SxExpr(f"(<> {inner})"))
 
 
 async def _h_post_entries_content(slug=None, **kw):
@@ -315,7 +315,7 @@ async def _h_post_entries_content(slug=None, **kw):
         await g.s.refresh(calendar, ["entries", "post"])
 
     # Associated entries list
-    assoc_html = await _render_associated_entries(all_calendars, associated_entry_ids, post_slug)
+    assoc_html = _render_associated_entries(all_calendars, associated_entry_ids, post_slug)
 
     # Calendar browser
     cal_items: list[str] = []
@@ -505,7 +505,7 @@ async def _h_post_edit_content(slug=None, **kw):
     from sqlalchemy.orm import selectinload
     from shared.infrastructure.data_client import fetch_data
     from shared.browser.app.csrf import generate_csrf_token
-    from shared.sx.helpers import render_to_sx
+    from shared.sx.helpers import sx_call
     from shared.sx.parser import SxExpr, serialize as sx_serialize
     from bp.post.admin.routes import _post_to_edit_dict
 
@@ -584,9 +584,9 @@ async def _h_post_edit_content(slug=None, **kw):
     parts: list[str] = []
 
     if save_error:
-        parts.append(await render_to_sx("blog-editor-error", error=save_error))
+        parts.append(sx_call("blog-editor-error", error=save_error))
 
-    parts.append(await render_to_sx("blog-editor-edit-form",
+    parts.append(sx_call("blog-editor-edit-form",
         csrf=csrf,
         updated_at=str(updated_at),
         title_val=title_val,
@@ -603,9 +603,9 @@ async def _h_post_edit_content(slug=None, **kw):
         footer_extra=footer_extra_sx,
     ))
 
-    parts.append(await render_to_sx("blog-editor-publish-js", already_emailed=already_emailed))
-    parts.append(await render_to_sx("blog-editor-styles", css_href=editor_css))
-    parts.append(await render_to_sx("sx-editor-styles"))
+    parts.append(sx_call("blog-editor-publish-js", already_emailed=already_emailed))
+    parts.append(sx_call("blog-editor-styles", css_href=editor_css))
+    parts.append(sx_call("sx-editor-styles"))
 
     init_js = (
         '(function() {'
@@ -705,10 +705,10 @@ async def _h_post_edit_content(slug=None, **kw):
         '  }, 50); }'
         '})();'
     )
-    parts.append(await render_to_sx("blog-editor-scripts",
+    parts.append(sx_call("blog-editor-scripts",
                          js_src=editor_js,
                          sx_editor_js_src=sx_editor_js,
                          init_js=init_js))
 
-    return await render_to_sx("blog-editor-panel",
+    return sx_call("blog-editor-panel",
         parts=SxExpr("(<> " + " ".join(parts) + ")"))