DRIFT fixes

[natoverse]

Hodgepodge of fixes and cleanups for DRIFT search.

• Fixes drift_k_followups not going all the way to prompt ([Bug]: DRIFT drift_k_followups Configuration Parameter Not Fully Utilized #2164)
• Adds DRIFT back to smoke tests to confirm inability to repo some intermittent issues (likely model or environment related, [Bug]: <title>'sources' ids in DRIFT SearchResult.context_data are misnumbered or hallucinated #1871, [Bug]: RuntimeError: <asyncio.locks.Semaphore object at 0xXXXXXXXXXX [locked]> is bound to a different event loop #2053, [Bug]: JSONDecodeError in DRIFT Search due to malformed LLM response (Invalid control character) #2163)
• Cleans out some unused params and other leftover cruft