fix(server): correlate OpenCode prompt admission

Stale cached user and status events could admit and complete a newly submitted OpenCode prompt. Generate the native message ID before submission and only advance admission when that exact message is observed.

Finding: R14

Implemented by GPT-5.6 Sol with Codex.
ee17bae99cJulius Marminge committed on 9/1/2026, 4:33:03 AMparent0bf1155
2 files changedLine totals unavailable