feat(fleet): launch workers through scheduler leases

[johnisag]

Summary

• Add Phase 3 fleet scheduling: lifecycle routes, scheduler leases, worker spawn/prompt delivery, pause/cancel cleanup, and recovery events.
• Coordinate fleet launches with dispatch caps, daily quota, budgets, live file claims, and cleanup-pending ownership.
• Improve the Fleet Management view with lifecycle controls, cancel confirmation, scoped scheduler feedback, worker identity, and spawn errors.

Validation

• npx tsc --noEmit
• npx prettier --check .
• npm test
• npm run build
• Local API smoke: GET http://127.0.0.1:3012/api/fleet/runs -> 200

Notes

• Build still reports the existing Turbopack NFT warning through app/api/git/clone/route.ts and next.config.ts.
• The local multi-agent review tool was unavailable after the session resumed; the prior four-reviewer findings were applied and rechecked manually before commit.