New command that spawns background agents to work on multiple
issues simultaneously, each in an isolated git worktree.
- commands/spawn-issues.md: Entry point, parses args, spawns agents
- agents/issue-worker/agent.md: Autonomous agent that implements
a single issue (worktree setup, implement, PR, cleanup)
Worktrees are automatically cleaned up after PR creation.
Branch remains on remote for follow-up work if needed.
Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
