cloud postgres delete --json returns raw API envelope instead of resource object

Discovered during v0.4.2 post-merge stress testing.

## Repro

```
chctl cloud postgres delete <id> --json
```

## Actual

`{"status":200,"requestId":"..."}` — the raw API envelope.

## Expected

Consistent with every other `cloud postgres` subcommand, `--json` should emit the resource object (or a structured deletion confirmation), not the raw envelope.