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>

sx/sxc/pages/utils.py

@@ -2,15 +2,15 @@
 from __future__ import annotations
 
 from shared.sx.helpers import (
-    render_to_sx, SxExpr,
+    sx_call, SxExpr,
 )
 
 
-async def _nav_items_sx(items: list[tuple[str, str]], current: str | None = None) -> str:
+def _nav_items_sx(items: list[tuple[str, str]], current: str | None = None) -> str:
     """Build nav link items as sx."""
     parts = []
     for label, href in items:
-        parts.append(await render_to_sx("nav-link",
+        parts.append(sx_call("nav-link",
             href=href, label=label,
             is_selected="true" if current == label else None,
             select_colours="aria-selected:bg-violet-200 aria-selected:text-violet-900",
@@ -18,54 +18,54 @@ async def _nav_items_sx(items: list[tuple[str, str]], current: str | None = None
     return "(<> " + " ".join(parts) + ")"
 
 
-async def _doc_nav_sx(items: list[tuple[str, str]], current: str) -> str:
+def _doc_nav_sx(items: list[tuple[str, str]], current: str) -> str:
     """Build the in-page doc navigation pills."""
     items_sx = " ".join(
         f'(list "{label}" "{href}")'
         for label, href in items
     )
-    return await render_to_sx("doc-nav", items=SxExpr(f"(list {items_sx})"), current=current)
+    return sx_call("doc-nav", items=SxExpr(f"(list {items_sx})"), current=current)
 
 
-async def _attr_table_sx(title: str, attrs: list[tuple[str, str, bool]]) -> str:
+def _attr_table_sx(title: str, attrs: list[tuple[str, str, bool]]) -> str:
     """Build an attribute reference table."""
     from content.pages import ATTR_DETAILS
     rows = []
     for attr, desc, exists in attrs:
         href = f"/reference/attributes/{attr}" if exists and attr in ATTR_DETAILS else None
-        rows.append(await render_to_sx("doc-attr-row", attr=attr, description=desc,
+        rows.append(sx_call("doc-attr-row", attr=attr, description=desc,
                            exists="true" if exists else None,
                            href=href))
     rows_sx = "(<> " + " ".join(rows) + ")"
-    return await render_to_sx("doc-attr-table", title=title, rows=SxExpr(rows_sx))
+    return sx_call("doc-attr-table", title=title, rows=SxExpr(rows_sx))
 
 
-async def _headers_table_sx(title: str, headers: list[tuple[str, str, str]]) -> str:
+def _headers_table_sx(title: str, headers: list[tuple[str, str, str]]) -> str:
     """Build a headers reference table."""
     rows = []
     for name, value, desc in headers:
-        rows.append(await render_to_sx("doc-headers-row",
+        rows.append(sx_call("doc-headers-row",
                            name=name, value=value, description=desc))
     rows_sx = "(<> " + " ".join(rows) + ")"
-    return await render_to_sx("doc-headers-table", title=title, rows=SxExpr(rows_sx))
+    return sx_call("doc-headers-table", title=title, rows=SxExpr(rows_sx))
 
 
-async def _primitives_section_sx() -> str:
+def _primitives_section_sx() -> str:
     """Build the primitives section."""
     from content.pages import PRIMITIVES
     parts = []
     for category, prims in PRIMITIVES.items():
         prims_sx = " ".join(f'"{p}"' for p in prims)
-        parts.append(await render_to_sx("doc-primitives-table",
+        parts.append(sx_call("doc-primitives-table",
             category=category,
             primitives=SxExpr(f"(list {prims_sx})")))
     return " ".join(parts)
 
 
-async def _sx_header_sx(nav: str | None = None, *, child: str | None = None) -> str:
+def _sx_header_sx(nav: str | None = None, *, child: str | None = None) -> str:
     """Build the sx docs menu-row."""
-    label_sx = await render_to_sx("sx-docs-label")
-    return await render_to_sx("menu-row-sx",
+    label_sx = sx_call("sx-docs-label")
+    return sx_call("menu-row-sx",
         id="sx-row", level=1, colour="violet",
         link_href="/", link_label="sx",
         link_label_content=SxExpr(label_sx),
@@ -75,40 +75,40 @@ async def _sx_header_sx(nav: str | None = None, *, child: str | None = None) ->
     )
 
 
-async def _docs_nav_sx(current: str | None = None) -> str:
+def _docs_nav_sx(current: str | None = None) -> str:
     from content.pages import DOCS_NAV
-    return await _nav_items_sx(DOCS_NAV, current)
+    return _nav_items_sx(DOCS_NAV, current)
 
 
-async def _reference_nav_sx(current: str | None = None) -> str:
+def _reference_nav_sx(current: str | None = None) -> str:
     from content.pages import REFERENCE_NAV
-    return await _nav_items_sx(REFERENCE_NAV, current)
+    return _nav_items_sx(REFERENCE_NAV, current)
 
 
-async def _protocols_nav_sx(current: str | None = None) -> str:
+def _protocols_nav_sx(current: str | None = None) -> str:
     from content.pages import PROTOCOLS_NAV
-    return await _nav_items_sx(PROTOCOLS_NAV, current)
+    return _nav_items_sx(PROTOCOLS_NAV, current)
 
 
-async def _examples_nav_sx(current: str | None = None) -> str:
+def _examples_nav_sx(current: str | None = None) -> str:
     from content.pages import EXAMPLES_NAV
-    return await _nav_items_sx(EXAMPLES_NAV, current)
+    return _nav_items_sx(EXAMPLES_NAV, current)
 
 
-async def _essays_nav_sx(current: str | None = None) -> str:
+def _essays_nav_sx(current: str | None = None) -> str:
     from content.pages import ESSAYS_NAV
-    return await _nav_items_sx(ESSAYS_NAV, current)
+    return _nav_items_sx(ESSAYS_NAV, current)
 
 
-async def _main_nav_sx(current_section: str | None = None) -> str:
+def _main_nav_sx(current_section: str | None = None) -> str:
     from content.pages import MAIN_NAV
-    return await _nav_items_sx(MAIN_NAV, current_section)
+    return _nav_items_sx(MAIN_NAV, current_section)
 
 
-async def _sub_row_sx(sub_label: str, sub_href: str, sub_nav: str,
+def _sub_row_sx(sub_label: str, sub_href: str, sub_nav: str,
                 selected: str = "") -> str:
     """Build the level-2 sub-section menu-row."""
-    return await render_to_sx("menu-row-sx",
+    return sx_call("menu-row-sx",
         id="sx-sub-row", level=2, colour="violet",
         link_href=sub_href, link_label=sub_label,
         selected=selected or None,