Stabilize agent runtime terminal lifecycle

[piorpua]

Summary

• Consolidate ACP and Aionrs terminal ownership so each turn resolves through a single terminal lifecycle.
• Downgrade send_error_rx to a fallback path instead of a normal competing terminal source.
• Add runtime lifecycle gates for deleting conversations so active-turn cleanup skips DB finalization after deletion.
• Suppress raw ACP SDK and aionrs debug payload logs while keeping structured lifecycle observability.

Verification

• just push -u origin round-1-terminal-lifecycle
• cargo nextest run --workspace: 5841 passed, 18 skipped