fix(workflow): detect duplicate trigger paths when first node has no id

validate_trigger_paths used seen_paths.get(trigger_path) and treated a None
result as "path not seen yet". But None is also what node.get("id") returns
for a node without an id, so when the first trigger node sharing a path had no
id, it was stored as None and every later node with the same path was silently
accepted as unique — duplicate trigger paths slipped through validation.

Use a membership test (trigger_path not in seen_paths) so "first occurrence"
and "node_id happens to be None" are no longer conflated. Behavior is
unchanged for nodes that have ids.

Adds a regression test that fails before and passes after.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

api/services/workflow/trigger_paths.py

@@ -127,8 +127,7 @@ def validate_trigger_paths(
                 )
             )
 
-        first_node_id = seen_paths.get(trigger_path)
-        if first_node_id is None:
+        if trigger_path not in seen_paths:
             seen_paths[trigger_path] = node_id
         else:
             issues.append(

api/tests/test_trigger_path_validation.py

@@ -54,3 +54,37 @@ def test_validate_trigger_paths_rejects_long_and_duplicate_paths():
         in messages
     )
     assert "Trigger path is duplicated in this workflow." in messages
+
+
+def test_validate_trigger_paths_detects_duplicate_when_first_node_has_no_id():
+    """A duplicate trigger path must be flagged even when the first node sharing
+    that path has no ``id`` (``node.get("id")`` is None).
+
+    Regression: the duplicate check previously used ``seen_paths.get(path)`` and
+    treated a ``None`` result as "not seen yet", so a first node with a missing
+    id (stored as None) made every later node with the same path slip through
+    undetected.
+    """
+    workflow_definition = {
+        "nodes": [
+            # No "id" key -> node_id resolves to None.
+            {"type": "trigger", "data": {"trigger_path": "sales_agent"}},
+            {
+                "id": "trigger-2",
+                "type": "trigger",
+                "data": {"trigger_path": "sales_agent"},
+            },
+        ],
+        "edges": [],
+    }
+
+    issues = validate_trigger_paths(workflow_definition)
+    messages = [issue.message for issue in issues]
+
+    assert "Trigger path is duplicated in this workflow." in messages
+    duplicate_issue = next(
+        issue
+        for issue in issues
+        if issue.message == "Trigger path is duplicated in this workflow."
+    )
+    assert duplicate_issue.node_id == "trigger-2"