Define sandbox site state seeding model

[chubes4]

Gap

Sandbox Runtime needs a way to seed the disposable WordPress environment from a parent site or selected source, beyond a blank Playground install.

Goal

Support explicit site/source seeding modes for coding tasks.

Acceptance direction

• Define supported seed modes: blank WP, current site snapshot, selected plugin/theme, repo checkout, fixtures, or blueprint.
• Keep parent-site data minimization explicit.
• Support WordPress options/content/media subsets where needed.
• Record seed provenance in artifacts.
• Avoid copying secrets or private content unless explicitly scoped.
• Make seed failures visible before agent execution starts.

Notes

This is required for flows like custom plugin development against a user's real site shape without mutating production.