* fix: disable duplicate trigger nodes in workflow builder
AddNodePanel: disable trigger buttons and show tooltip when a trigger
already exists on the canvas, using bySpecName to identify trigger-
category specs from the live node list.
useWorkflowState: preflight in saveWorkflow rejects saves with multiple
trigger nodes via a sonner toast before the network request is made.
text_chat_session_service: include the original exception message in
TextChatSessionExecutionError so the HTTP 500 detail surfaces the root
cause without DB inspection.
Closes#378
* style: format test_text_chat_session_service.py with ruff
* chore: retrigger CI checks
* fix(workflow): enforce node instance constraints
---------
Co-authored-by: Abhishek Kumar <abhishek@a6k.me>
