Fix sync IO primitives unreachable from sx_ref.py evaluator

app-url, asset-url, config, jinja-global, relations-from are declared
as IO in boundary.sx but called inline in .sx code (inside let/filter).
async_eval_ref.py only intercepts IO at the top level — nested calls
fall through to sx_ref.eval_expr which couldn't find them.

Register sync bridge wrappers directly in _PRIMITIVES (bypassing
@register_primitive validation since they're boundary.sx, not
primitives.sx). Both async and sync eval paths now work.

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

shared/sx/primitives.py

@@ -558,3 +558,55 @@ def prim_merge_styles(*styles: Any) -> Any:
     if len(valid) == 1:
         return valid[0]
     return merge_styles(valid)
+
+
+# ---------------------------------------------------------------------------
+# Sync IO bridge primitives
+#
+# These are declared in boundary.sx (I/O tier), NOT primitives.sx.
+# They bypass @register_primitive validation because they aren't pure.
+# But they must be evaluator-visible because they're called inline in .sx
+# code (inside let, filter, etc.) where the async IO interceptor can't
+# reach them — particularly in async_eval_ref.py which only intercepts
+# IO at the top level.
+#
+# The async evaluators also intercept these via IO_PRIMITIVES, so the
+# async path works too. This registration ensures the sync fallback works.
+# ---------------------------------------------------------------------------
+
+def _bridge_app_url(service, *path_parts):
+    from shared.infrastructure.urls import app_url
+    path = str(path_parts[0]) if path_parts else "/"
+    return app_url(str(service), path)
+
+def _bridge_asset_url(*path_parts):
+    from shared.infrastructure.urls import asset_url
+    path = str(path_parts[0]) if path_parts else ""
+    return asset_url(path)
+
+def _bridge_config(key):
+    from shared.config import config
+    cfg = config()
+    return cfg.get(str(key))
+
+def _bridge_jinja_global(key, *default):
+    from quart import current_app
+    d = default[0] if default else None
+    return current_app.jinja_env.globals.get(str(key), d)
+
+def _bridge_relations_from(entity_type):
+    from shared.sx.relations import relations_from
+    return [
+        {
+            "name": d.name, "from_type": d.from_type, "to_type": d.to_type,
+            "cardinality": d.cardinality, "nav": d.nav,
+            "nav_icon": d.nav_icon, "nav_label": d.nav_label,
+        }
+        for d in relations_from(str(entity_type))
+    ]
+
+_PRIMITIVES["app-url"] = _bridge_app_url
+_PRIMITIVES["asset-url"] = _bridge_asset_url
+_PRIMITIVES["config"] = _bridge_config
+_PRIMITIVES["jinja-global"] = _bridge_jinja_global
+_PRIMITIVES["relations-from"] = _bridge_relations_from