Fix 4163 Ultrawork Notepad

Bootstrap

• Tier: HEAVY.
• Justification: The change targets session continuation and background-task race behavior.
• Worktree: /Users/yeongyu/local-workspaces/omo/.local-ignore/pr-worktrees/fix-4163.
• Branch: expected sisyphus-bot/fix-4163.

Skills

• work-with-pr: required because the deliverable is a PR merged or auto-merge armed against dev.
• opencode-qa: required because the change touches OpenCode plugin hook behavior.
• omo-programming: required for TypeScript source and test edits.
• commit and git-master: required for atomic commits and safe branch/PR git operations.
• review-work: required as a blocking post-implementation HEAVY review gate.

Success Criteria

1. Failing-first proof confirms the race on current dev: active children false, pending parent wake true, incomplete todos, and the enforcer must not inject.
2. Minimal fix strengthens existing gates only, with no new session.prompt or session.promptAsync route.
3. Required tests pass: todo-continuation-enforcer suite, prompt async route audit, and typecheck.
4. OpenCode QA evidence is captured under this directory, or a documented deterministic-race justification explains why a live repro is impractical.
5. A reviewer-readable PR targeting dev is pushed and auto-merge is enabled with merge commit semantics.

Evidence Index

• Setup rerun with PATH="$HOME/.bun/bin:$PATH" bash script/agent/setup.sh: passed after initial PATH-only bun lookup failure.