Convert all 23 register_custom_layout calls to register_sx_layout across 6 services

Layout defcomps are now fully self-contained via IO-primitive auto-fetch
macros, eliminating Python layout functions that manually threaded context
values through SxExpr wrappers.

Services converted:
- Federation (1 layout): social
- Blog (7 layouts): blog, blog-settings, blog-cache, blog-snippets,
  blog-menu-items, blog-tag-groups, blog-tag-group-edit
- SX docs (2 layouts): sx, sx-section
- Cart (2 layouts): cart-page, cart-admin + orders/order-detail
- Events (9 layouts): calendar-admin, slots, slot, day-admin, entry,
  entry-admin, ticket-types, ticket-type, markets
- Market (2 layouts): market, market-admin

New IO primitives added to shared/sx/primitives_io.py:
- federation-actor-ctx, cart-page-ctx, request-view-args
- events-calendar-ctx, events-day-ctx, events-entry-ctx,
  events-slot-ctx, events-ticket-type-ctx
- market-header-ctx (pre-builds desktop/mobile nav as SxExpr)

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

market/sxc/pages/layouts.py

@@ -4,15 +4,9 @@ from __future__ import annotations
 from typing import Any
 
 from shared.sx.parser import SxExpr
-from shared.sx.helpers import (
-    sx_call,
-    post_header_sx as _post_header_sx,
-    post_admin_header_sx,
-    oob_header_sx as _oob_header_sx,
-    header_child_sx,
-)
+from shared.sx.helpers import sx_call
 
-from .utils import _set_prices, _price_str, _clear_deeper_oob
+from .utils import _set_prices, _price_str
 
 
 # ---------------------------------------------------------------------------
@@ -272,62 +266,14 @@ def _product_admin_header_sx(ctx: dict, d: dict, *, oob: bool = False) -> str:
     )
 
 
-# ---------------------------------------------------------------------------
-# Market admin header
-# ---------------------------------------------------------------------------
-
-async def _market_admin_header_sx(ctx: dict, *, oob: bool = False, selected: str = "") -> str:
-    """Build market admin header row -- delegates to shared helper."""
-    slug = (ctx.get("post") or {}).get("slug", "")
-    return await post_admin_header_sx(ctx, slug, oob=oob, selected=selected)
-
-
 # ===========================================================================
-# Layout registration
+# Layout registration — all layouts delegate to .sx defcomps
 # ===========================================================================
 
 def _register_market_layouts() -> None:
-    from shared.sx.layouts import register_custom_layout
-    register_custom_layout("market", _market_full, _market_oob, _market_mobile)
-    register_custom_layout("market-admin", _market_admin_full, _market_admin_oob)
-
-
-async def _market_full(ctx: dict, **kw: Any) -> str:
-    from shared.sx.helpers import render_to_sx_with_env
-    return await render_to_sx_with_env("market-browse-layout-full", {},
-        post_header=SxExpr(await _post_header_sx(ctx)),
-        market_header=SxExpr(_market_header_sx(ctx)))
-
-
-async def _market_oob(ctx: dict, **kw: Any) -> str:
-    oob_hdr = await _oob_header_sx("post-header-child", "market-header-child",
-                             _market_header_sx(ctx))
-    return sx_call("market-browse-layout-oob",
-        oob_header=SxExpr(oob_hdr),
-        post_header_oob=SxExpr(await _post_header_sx(ctx, oob=True)),
-        clear_oob=SxExpr(_clear_deeper_oob("post-row", "post-header-child",
-                               "market-row", "market-header-child")))
-
-
-def _market_mobile(ctx: dict, **kw: Any) -> str:
-    return _mobile_nav_panel_sx(ctx)
-
-
-async def _market_admin_full(ctx: dict, **kw: Any) -> str:
-    from shared.sx.helpers import render_to_sx_with_env
-    selected = kw.get("selected", "")
-    return await render_to_sx_with_env("market-admin-layout-full", {},
-        post_header=SxExpr(await _post_header_sx(ctx)),
-        market_header=SxExpr(_market_header_sx(ctx)),
-        admin_header=SxExpr(await _market_admin_header_sx(ctx, selected=selected)))
-
-
-async def _market_admin_oob(ctx: dict, **kw: Any) -> str:
-    selected = kw.get("selected", "")
-    return sx_call("market-admin-layout-oob",
-        market_header_oob=SxExpr(_market_header_sx(ctx, oob=True)),
-        admin_oob_header=SxExpr(await _oob_header_sx("market-header-child", "market-admin-header-child",
-                              await _market_admin_header_sx(ctx, selected=selected))),
-        clear_oob=SxExpr(_clear_deeper_oob("post-row", "post-header-child",
-                               "market-row", "market-header-child",
-                               "market-admin-row", "market-admin-header-child")))
+    from shared.sx.layouts import register_sx_layout
+    register_sx_layout("market",
+                       "market-browse-layout-full", "market-browse-layout-oob",
+                       "market-browse-layout-mobile")
+    register_sx_layout("market-admin",
+                       "market-admin-layout-full", "market-admin-layout-oob")