Fix NIL leaking into Python service calls, add mobile navigation menu

Strip NIL values at I/O primitive boundaries (frag, query, action, service)
to prevent _Nil objects from reaching Python code that expects None. Add
mobile_nav_sx() helper that auto-populates the hamburger menu from nav_tree
and auth_menu context fragments when no menu slot is provided.

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

shared/sx/primitives_io.py

@@ -107,6 +107,12 @@ async def execute_io(
 # Individual handlers
 # ---------------------------------------------------------------------------
 
+def _clean_kwargs(kwargs: dict[str, Any]) -> dict[str, Any]:
+    """Strip None and NIL values from kwargs for Python interop."""
+    from .types import NIL
+    return {k: v for k, v in kwargs.items() if v is not None and v is not NIL}
+
+
 async def _io_frag(
     args: list[Any], kwargs: dict[str, Any], ctx: RequestContext
 ) -> str:
@@ -115,7 +121,7 @@ async def _io_frag(
         raise ValueError("frag requires service and fragment type")
     service = str(args[0])
     frag_type = str(args[1])
-    params = {k: v for k, v in kwargs.items() if v is not None}
+    params = _clean_kwargs(kwargs)
 
     from shared.infrastructure.fragments import fetch_fragment
     return await fetch_fragment(service, frag_type, params=params or None)
@@ -129,7 +135,7 @@ async def _io_query(
         raise ValueError("query requires service and query name")
     service = str(args[0])
     query_name = str(args[1])
-    params = {k: v for k, v in kwargs.items() if v is not None}
+    params = _clean_kwargs(kwargs)
 
     from shared.infrastructure.data_client import fetch_data
     return await fetch_data(service, query_name, params=params or None)
@@ -143,7 +149,7 @@ async def _io_action(
         raise ValueError("action requires service and action name")
     service = str(args[0])
     action_name = str(args[1])
-    payload = {k: v for k, v in kwargs.items() if v is not None}
+    payload = _clean_kwargs(kwargs)
 
     from shared.infrastructure.actions import call_action
     return await call_action(service, action_name, payload=payload or None)
@@ -195,8 +201,12 @@ async def _io_service(
     if method is None:
         raise RuntimeError(f"Service has no method: {method_name}")
 
-    # Convert kwarg keys from kebab-case to snake_case
-    clean_kwargs = {k.replace("-", "_"): v for k, v in kwargs.items()}
+    # Convert kwarg keys from kebab-case to snake_case, NIL → None
+    from .types import NIL
+    clean_kwargs = {
+        k.replace("-", "_"): (None if v is NIL else v)
+        for k, v in kwargs.items()
+    }
     from quart import g
     result = await method(g.s, **clean_kwargs)