Replace env free-variable threading with IO-primitive auto-fetch macros

Layout components now self-resolve context (cart-mini, auth-menu, nav-tree,
rights, URLs) via new IO primitives (root-header-ctx, select-colours,
account-nav-ctx, app-rights) and defmacro wrappers (~root-header-auto,
~auth-header-row-auto, ~root-mobile-auto). This eliminates _ctx_to_env(),
HELPER_CSS_CLASSES, and verbose :key threading across all 10 services.

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

events/sxc/pages/utils.py

@@ -17,7 +17,8 @@ from shared.sx.parser import SxExpr
 
 def _clear_oob(*ids: str) -> str:
     """Generate OOB swaps to remove orphaned header rows/children."""
-    return "".join(f'(div :id "{i}" :hx-swap-oob "outerHTML")' for i in ids)
+    from shared.sx.helpers import sx_call
+    return "".join(sx_call("clear-oob-div", id=i) for i in ids)
 
 
 # All possible header row/child IDs at each depth (deepest first)