Problem

openclaw agent --json --deliver currently has no machine-readable indication of whether delivery succeeded, failed, or was skipped. The JSON envelope contains payloads and meta but no delivery status.

This means automation consuming --json output cannot detect silent delivery failures — the exact scenario that #53961 adds diagnostic logging for in non-JSON mode.

Desired behavior

Add a deliveryStatus field to the JSON output envelope when --deliver is used:

{
  "payloads": [...],
  "meta": {...},
  "deliveryStatus": {
    "requested": true,
    "attempted": true,
    "succeeded": false,
    "error": true
  }
}

Design considerations

The JSON envelope is currently emitted before delivery (so stdout stays machine-readable even if delivery throws). Adding deliveryStatus requires either:

1. Deferring JSON output until after delivery — but then late throws (non-bestEffort API timeouts) would skip JSON output entirely, breaking scripts
2. Emitting two JSON objects — payload first, status second — but this changes the single-object contract
3. Wrapping delivery in try/finally to ensure JSON is always emitted, with status reflecting the outcome
4. Separate status line — a second JSON line (JSONL-style) with just the delivery result

Each approach has trade-offs around backward compatibility, error handling, and parseability. Needs design discussion before implementation.

Additional edge cases to address

• Partial best-effort delivery (some payloads succeed, others fail)
• No-payload runs (tool-only turns, heartbeat acks) where delivery is requested but nothing to send
• normalizeAgentCommandReplyPayloads() intentionally dropping silent-only payloads

Context

Related: #53961 (adds non-JSON diagnostic logging for silent delivery failures). The deliveryStatus object is already returned in the function's in-process return value — this issue is specifically about surfacing it in the stdout JSON output.