🤖 Task launch: a reactivation that prepends the brief can resend it after a durable-then-Err send

[ThomasK33]

Problem

After #5543, a reactivation that prepends a kept initial brief can still deliver it twice. The reactivation's own send can make its rows durable and then return Err (the same "durable, then Err" shape as U4 path A). taskPrompt then stays, with the launch's taskPromptSendId, which no history row carries. The next reawakening prepends the brief again.

This existed before #5543. formal/task-launch models the reawakening (React) as one atomic step, so it does not cover this.

Direction

Stamp a brief send id on the reactivation send that carries the kept prompt (mint one, store it as taskPromptSendId before the send, pass it as sendIdentities), so the existing lookup (isTaskBriefInHistory) recognizes that row too.

Smaller follow-ups from the #5543 review

• applyInterruptedTaskStatus (taskService.ts) clears taskPrompt but leaves taskPromptSendId. The id has no effect without a prompt; clear it for tidiness.
• Add one real-session test (real AgentSession + HistoryService) where a Stop rolls back the launch's brief row, and check that the reawakening then sends the brief once.

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Generated with xum • Model: anthropic:claude-opus-5-5 • Thinking: high

[ThomasK33]

Picked up by the issue coordinator: workspace workspace-67, branch fix/task-reactivation-brief-send-id

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Generated with xum • Model: anthropic:claude-opus-5-5 • Thinking: high

[ThomasK33]

Triage: A (one backend, no new persisted field: taskPromptSendId exists).

Plan: when reactivateInactiveAgentTask prepends a kept brief, it mints a fresh brief send id, stores it as taskPromptSendId in its existing attempt-commit CAS (only while the row still holds that brief), and passes the brief identity as sendIdentities through createWorkspaceTurn to the send (with skipOnSendCompaction, as the launch does). isTaskBriefInHistory then recognizes the reactivation row. The two smaller follow-ups are in scope too: applyInterruptedTaskStatus clears taskPromptSendId with taskPrompt, and one real-session test (real AgentSession and HistoryService) covers a Stop that rolls back the brief row. Test-first. A PR follows.

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Generated with xum • Model: anthropic:claude-opus-5-5 • Thinking: high

[ThomasK33]

Fixed by #5581, merged as 44b2201. The remaining duplicate-on-immediate-retry case (this backend's own turn lease) is tracked in #5588, with the fix ready on branch fix/5544-foreign-lease-narrowing.

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Generated with xum • Model: anthropic:claude-opus-5-5 • Thinking: high