sched: address R1 findings on shared traversal and resolver threading

tests/scheduling/test_schedule_expressions.py

@@ -111,6 +111,53 @@ def test_graph_only_path_is_invalid_in_schedule_bindings() -> None:
         )
 
 
+def test_nested_graph_path_is_invalid_in_schedule_bindings() -> None:
+    with pytest.raises(ValidationError):
+        ScheduleInputBinding.model_validate(
+            {
+                "target": "x",
+                "expression": {
+                    "kind": "object",
+                    "fields": {
+                        "nested": {"kind": "path", "path": "input.a"},
+                    },
+                },
+            }
+        )
+    with pytest.raises(ValidationError):
+        ScheduleInputBinding.model_validate(
+            {
+                "target": "x",
+                "expression": {
+                    "kind": "array",
+                    "items": [{"kind": "path", "path": "state.b"}],
+                },
+            }
+        )
+
+
+def test_nested_occurrence_is_invalid_in_graph_bindings() -> None:
+    from wf_core.models.input_bindings import (
+        ArrayExpression,
+        ObjectExpression,
+    )
+
+    with pytest.raises(ValidationError):
+        ArrayExpression.model_validate(
+            {
+                "kind": "array",
+                "items": [{"kind": "occurrence", "field": "scheduled_at"}],
+            }
+        )
+    with pytest.raises(ValidationError):
+        ObjectExpression.model_validate(
+            {
+                "kind": "object",
+                "fields": {"when": {"kind": "occurrence", "field": "scheduled_at"}},
+            }
+        )
+
+
 def test_invalid_field_rejected() -> None:
     with pytest.raises(ValidationError):
         ScheduleInputBinding.model_validate(
@@ -153,7 +200,7 @@ def test_invalid_resolved_input_fails_schema_check() -> None:
     resolved = resolve_schedule_input_bindings(
         [binding], occurrence=OCC, label="schedule s"
     )
-    with pytest.raises(Exception, match="count"):
+    with pytest.raises(WorkflowExecutionError, match="count"):
         validate_payload_against_schema(
             {"type": "object", "properties": {"count": {"type": "integer"}}},
             resolved,
@@ -161,10 +208,27 @@ def test_invalid_resolved_input_fails_schema_check() -> None:
         )
 
 
-def test_direct_schedule_expression_resolution_rejects_graph_paths() -> None:
+def test_direct_schedule_expression_resolves_literal() -> None:
     expr = ScheduleInputBinding.model_validate(
         {"target": "x", "expression": {"kind": "literal", "value": 1}}
     ).expression
     assert (
         resolve_schedule_expression(expr, occurrence=OCC, label="s", location="x") == 1
     )
+
+
+def test_graph_path_leaf_rejected_inside_schedule_traversal() -> None:
+    from wf_core.models.input_bindings import PathExpression
+
+    from wf_core.runtime.input_sources import MappingSourceResolver
+
+    graph_leaf = PathExpression.model_validate(
+        {"kind": "path", "path": "input.a"}
+    )
+    with pytest.raises(WorkflowExecutionError, match="graph paths are invalid"):
+        resolve_schedule_expression(
+            graph_leaf,  # type: ignore[arg-type]
+            occurrence=MappingSourceResolver(OCC),
+            label="s",
+            location="x",
+        )