agent runtime: persist headless run registry with status, heartbeat, and artifacts

[chubes4]

Problem

WP Codebox can run headless lab cells, but replacing fleet cooking needs a durable run registry rather than only a synchronous process plus temp artifact directory.

The orchestrator should be able to submit many Codebox runs, poll status, inspect logs/artifacts, resume from partial state when possible, and clean up safely later.

Desired shape

Add a durable headless run registry with:

• run_id for each Codebox task.
• Current status: queued, booting, running, collecting_artifacts, succeeded, failed, timed_out, cancelled.
• Heartbeat/last activity timestamp.
• Runtime metadata and preview info when relevant.
• Artifact bundle refs.
• Command log/transcript refs.
• Cleanup eligibility and retention metadata.
• Replay command or recipe reference.

Layer boundary

WP Codebox owns sandbox runtime state and artifact indexing. Homeboy should consume this through provider APIs/CLI output; it should not scrape temp dirs as the product path.

Acceptance criteria

• A caller can submit or start a headless run and receive a stable run_id.
• A caller can query status/artifacts after the original process exits or times out.
• Run metadata avoids leaking secrets.
• Cleanup can remove old runs without losing accepted/promoted evidence.

AI assistance

• AI assistance: Yes
• Tool(s): OpenCode (GPT-5.5)
• Used for: Drafting this issue from the Homeboy/WP Codebox fan-out proof.