When a draft carries the `__bugs_migrated` marker, publishing no longer copies the `bugs_closed` string. Instead, the review request's bug relations are set from the draft's and the review request is marked as migrated. Publishing records one change entry per affected tracker under `bugs:<id>` keys, with a label snapshot so history renders even if the tracker later goes away. The legacy `bugs_closed` entry is still written when the default tracker's view changes, for rbtools and the API. Publishing a string-driven draft over a migrated review request pops the review request's marker, reverting it to string-driven behavior so the fresh string is read. Testing Done: Ran unit tests.