## Why
Global deprecation notices can be delivered again by hidden threads, creating duplicate transcript entries.
## What changed
Skip incoming deprecation notices whose summary and details match a notice already in retained history. Preserve notices with different summaries or details, and allow notices to appear again after clearing history or rebuilding the transcript during a thread switch.
## Testing
Add a regression test and transcript snapshot covering repeated live and replayed notifications, an open transcript overlay, distinct notice content, and delivery after clearing history or switching threads.
GitOrigin-RevId: 9c0512f588dfb54f7934380119211b57b0df0ee4