After a crash with an ask_user prompt on screen, resuming the session shows the same prompt but it can't be answered or dismissed; rewinding is the only way out #5019

Describe the bug

If the CLI crashes or exits unexpectedly while an ask_user form is on screen, copilot --resume restores the session with that same form showing. The form doesn't respond: you can't select options, type an answer, submit, cancel or exit it.

The only way out is to rewind to an earlier turn. That causes three problems:

• At least one turn is lost.
• The agent has to redo the work from the rewound turn (tool calls, reads, analysis). That costs time and AI credits and may repeat side effects.
• The user has to remember what the prompt asked and re-state the context, because the rewind removes the prompt from history.

Steps to reproduce

1. Start an interactive session and give it a task where the agent calls ask_user, so a structured form is on screen.
2. While the form is showing, the CLI process crashes or is killed. We saw this with real crashes; killing the process should reproduce it.
3. Run copilot --resume and pick that session.
4. The same ask_user form appears but doesn't respond to input. Esc and Ctrl+C don't dismiss it.
5. The only recovery is rewinding (/rewind or Esc Esc) to a turn before the prompt.

Expected behavior

One of these, in order of preference:

1. The restored prompt works normally and the answer goes back to the pending tool call.
2. The CLI detects the orphaned ask_user call, since it has tool.execution_start but no tool.execution_complete. It then completes the call with a cancelled or interrupted result and returns control to the user without losing the turn. The agent can then re-ask.
3. At minimum, Esc or Ctrl+C cancels the restored prompt instead of leaving the session stuck.

Notes

• This looks like the same kind of problem as --resume replays orphaned permission.requested events (no matching permission.completed) after mid-prompt process death #4259 and Orphaned  permission.requested  event replays on every session resume, causing repeated directory-access prompts that can't be dismissed #4469: an interactive request left pending across a process death gets replayed on resume but can't be resolved. Those issues involve permission.requested; this one involves the ask_user tool call.
• Rewinding removes the orphaned tool.execution_start from events.jsonl, so afterwards there's no local trace of the problem. That makes it hard to attach logs after the fact.

Environment

• CLI: 1.0.88 (now on 1.0.89; not yet re-observed)
• OS: Windows 11 (10.0.26200)
• Shell: PowerShell 7.6.6
• Terminal: VS Code integrated terminal
• Model: claude-opus-5.5