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>

test/sxc/pages/renders.py

@@ -5,7 +5,7 @@ import os
 from datetime import datetime
 
 from shared.sx.jinja_bridge import load_service_components
-from shared.sx.helpers import render_to_sx, SxExpr, render_to_sx_with_env, _ctx_to_env, full_page_sx
+from shared.sx.helpers import render_to_sx, SxExpr, render_to_sx_with_env, full_page_sx
 
 # Load test-specific .sx components at import time
 load_service_components(os.path.dirname(os.path.dirname(os.path.dirname(__file__))))
@@ -99,7 +99,7 @@ async def render_dashboard_page_sx(ctx: dict, result: dict | None,
     inner = await render_to_sx("test-results-partial",
         summary_data=summary_data, sections=sections, has_failures=has_failures)
     content = await render_to_sx("test-results-wrap", running=running, inner=SxExpr(inner))
-    hdr = await render_to_sx_with_env("test-layout-full", _ctx_to_env(ctx),
+    hdr = await render_to_sx_with_env("test-layout-full", {},
         services=_service_list(),
         active_service=active_service,
     )
@@ -131,7 +131,7 @@ async def render_results_partial_sx(result: dict | None, running: bool,
 
 async def render_test_detail_page_sx(ctx: dict, test: dict) -> str:
     """Full page: test detail (sx wire format)."""
-    hdr = await render_to_sx_with_env("test-detail-layout-full", _ctx_to_env(ctx),
+    hdr = await render_to_sx_with_env("test-detail-layout-full", {},
         services=_service_list(),
         test_nodeid=test["nodeid"],
         test_label=test["nodeid"].rsplit("::", 1)[-1],