TaskUpdate/TaskList task IDs do not survive a session resume

Summary

After a session is resumed (e.g. via "Continue" / resuming an interrupted session), TaskUpdate on a task ID that was valid earlier in the same session returns Task not found. The task list appears to have re-listed with reset/renumbered IDs. Status updates queued for end-of-work then fail to land, so the work completes untracked.

Steps to reproduce

1. In a session, TaskCreate several tasks (IDs 1–5).
2. TaskUpdate some of them to in_progress / completed — works fine.
3. The session is resumed (interruption, then "Continue from where you left off").
4. TaskUpdate {taskId: "5", status: "completed"} → Task not found.

Expected

Task IDs remain stable across a session resume; updates to previously-created task IDs land.

Actual

TaskUpdate returns Task not found for a task ID that was valid pre-resume; the task list appears renumbered/reset.

Impact

Minor / non-blocking, but end-of-session status reconciliation can't complete — the final task cannot be marked done, so the work finishes untracked.

Environment

• Claude Code (CLI), macOS (Darwin 25.5.0)
• Model: Opus 4.8 (1M context)