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>

shared/sx/layouts.py

@@ -2,8 +2,8 @@
 Named layout presets for defpage.
 
 Each layout generates header rows for full-page and OOB rendering.
-Layouts wrap existing helper functions from ``shared.sx.helpers`` so
-defpage can reference them by name (e.g. ``:layout :root``).
+Built-in layouts delegate to .sx defcomps via ``register_sx_layout``.
+Services register custom layouts via ``register_custom_layout``.
 
 Layouts are registered in ``_LAYOUT_REGISTRY`` and looked up by
 ``get_layout()`` at request time.
@@ -13,12 +13,6 @@ from __future__ import annotations
 
 from typing import Any, Callable, Awaitable
 
-from .helpers import (
-    root_header_sx, post_header_sx, post_admin_header_sx,
-    oob_header_sx,
-    mobile_menu_sx, mobile_root_nav_sx,
-    post_mobile_nav_sx, post_admin_mobile_nav_sx,
-)
 
 
 # ---------------------------------------------------------------------------
@@ -83,57 +77,8 @@ def get_layout(name: str) -> Layout | None:
     return _LAYOUT_REGISTRY.get(name)
 
 
-# ---------------------------------------------------------------------------
-# Built-in layouts
-# ---------------------------------------------------------------------------
-
-async def _post_full(ctx: dict, **kw: Any) -> str:
-    root_hdr = await root_header_sx(ctx)
-    post_hdr = await post_header_sx(ctx)
-    return "(<> " + root_hdr + " " + post_hdr + ")"
-
-
-async def _post_oob(ctx: dict, **kw: Any) -> str:
-    post_hdr = await post_header_sx(ctx, oob=True)
-    # Also replace #post-header-child (empty — clears any nested admin rows)
-    child_oob = await oob_header_sx("post-header-child", "", "")
-    return "(<> " + post_hdr + " " + child_oob + ")"
-
-
-async def _post_admin_full(ctx: dict, **kw: Any) -> str:
-    slug = ctx.get("post", {}).get("slug", "")
-    selected = kw.get("selected", "")
-    root_hdr = await root_header_sx(ctx)
-    admin_hdr = await post_admin_header_sx(ctx, slug, selected=selected)
-    post_hdr = await post_header_sx(ctx, child=admin_hdr)
-    return "(<> " + root_hdr + " " + post_hdr + ")"
-
-
-async def _post_admin_oob(ctx: dict, **kw: Any) -> str:
-    slug = ctx.get("post", {}).get("slug", "")
-    selected = kw.get("selected", "")
-    post_hdr = await post_header_sx(ctx, oob=True)
-    admin_hdr = await post_admin_header_sx(ctx, slug, selected=selected)
-    admin_oob = await oob_header_sx("post-header-child", "post-admin-header-child", admin_hdr)
-    return "(<> " + post_hdr + " " + admin_oob + ")"
-
-
-async def _post_mobile(ctx: dict, **kw: Any) -> str:
-    return mobile_menu_sx(await post_mobile_nav_sx(ctx), await mobile_root_nav_sx(ctx))
-
-
-async def _post_admin_mobile(ctx: dict, **kw: Any) -> str:
-    slug = ctx.get("post", {}).get("slug", "")
-    selected = kw.get("selected", "")
-    return mobile_menu_sx(
-        await post_admin_mobile_nav_sx(ctx, slug, selected),
-        await post_mobile_nav_sx(ctx),
-        await mobile_root_nav_sx(ctx),
-    )
-
-
-register_layout(Layout("post", _post_full, _post_oob, _post_mobile))
-register_layout(Layout("post-admin", _post_admin_full, _post_admin_oob, _post_admin_mobile))
+# Built-in post/post-admin layouts are registered below via register_sx_layout,
+# after that function is defined.
 
 
 # ---------------------------------------------------------------------------
@@ -153,27 +98,29 @@ def register_sx_layout(name: str, full_defcomp: str, oob_defcomp: str,
         register_sx_layout("account", "account-layout-full",
                            "account-layout-oob", "account-layout-mobile")
     """
-    from .helpers import render_to_sx_with_env
+    from .helpers import _render_to_sx_with_env
 
     async def full_fn(ctx: dict, **kw: Any) -> str:
         env = {k.replace("_", "-"): v for k, v in kw.items()}
-        return await render_to_sx_with_env(full_defcomp, env)
+        return await _render_to_sx_with_env(full_defcomp, env)
 
     async def oob_fn(ctx: dict, **kw: Any) -> str:
         env = {k.replace("_", "-"): v for k, v in kw.items()}
-        return await render_to_sx_with_env(oob_defcomp, env)
+        return await _render_to_sx_with_env(oob_defcomp, env)
 
     mobile_fn = None
     if mobile_defcomp:
         async def mobile_fn(ctx: dict, **kw: Any) -> str:
             env = {k.replace("_", "-"): v for k, v in kw.items()}
-            return await render_to_sx_with_env(mobile_defcomp, env)
+            return await _render_to_sx_with_env(mobile_defcomp, env)
 
     register_layout(Layout(name, full_fn, oob_fn, mobile_fn))
 
 
-# Register built-in "root" layout via .sx defcomps
+# Register built-in layouts via .sx defcomps
 register_sx_layout("root", "layout-root-full", "layout-root-oob", "layout-root-mobile")
+register_sx_layout("post", "layout-post-full", "layout-post-oob", "layout-post-mobile")
+register_sx_layout("post-admin", "layout-post-admin-full", "layout-post-admin-oob", "layout-post-admin-mobile")
 
 
 # ---------------------------------------------------------------------------