fix(cli): simplify service registration lease

[opencode-agent]

Summary

• publish the managed-service registration exactly once after the exact-port bind
• shut down the server when its registration is missing, corrupt, or no longer matches, without repairing it
• close the listener before conditionally removing only the instance-owned registration
• remove the unused startedAt registration generation from client Info

Validation

• bun test test/service.test.ts --timeout 120000 (packages/cli, 15 passed)
• bun test test/service.test.ts test/promise-service.test.ts --timeout 30000 (packages/client, 15 passed)
• GOMAXPROCS=2 bun typecheck (packages/server)
• GOMAXPROCS=2 bun typecheck (packages/cli)
• GOMAXPROCS=2 bun typecheck (packages/client)
• Prettier check on all changed files

Requested by: @thdxr (Dax Raad via Slack)