fix(kanban): use 'is not None' check for max_runtime_seconds in create_task

max_runtime_seconds=0 was being silently coerced to None due to a falsy
check (if max_runtime_seconds). Zero is a valid value that causes the
dispatcher to immediately time out a task. The adjacent max_retries
parameter already used the correct 'is not None' pattern.

Fixes the inconsistency by aligning max_runtime_seconds with max_retries.

hermes_cli/kanban_db.py

@@ -1408,7 +1408,7 @@ def create_task(
                         workspace_path,
                         tenant,
                         idempotency_key,
-                        int(max_runtime_seconds) if max_runtime_seconds else None,
+                        int(max_runtime_seconds) if max_runtime_seconds is not None else None,
                         json.dumps(skills_list) if skills_list is not None else None,
                         int(max_retries) if max_retries is not None else None,
                     ),