Finish durable abnormal query termination and compaction handling

[BunsDev]

WIP branch: https://github.com/OpenCoven/coven-code/tree/wip/post-pr175-stream-query-hardening

Follow-up scope:

• substantive stall/cancel durability
• unmatched tool closure
• proactive/reactive/emergency compaction cancellation
• retry output without empty durable assistants
• TUI DurableMessage handling
• full gates/reviews