Empty sessions (message_count=0) created by interrupted flows (e.g.,
desktop session creation that never received a message) would block
session rename attempts even though they were invisible in the UI.
Changes:
- Updated title uniqueness index to exclude sessions with 0 messages
- Modified _set_session_title conflict check to skip empty sessions
- Added migration to drop and rebuild the index with new filter
- Added regression test for ghost session rename blocking
Fixes#81888
(cherry picked from commit a28e084278694a3b7e5f0adbfae90b14ac575db2)
fb4aac296b