Closed as superseded by durable Objective and design documentation.

This Ticket was a broad Plugin runtime/surface/host API design record rather than a concrete implementation task. The useful design decisions have been moved into durable roadmap/design context:
- Objective `00001KVG0HR9M` (`Plugin platform roadmap`) now owns the overall Plugin roadmap and sequencing context.
- `docs/design/plugin-component-model.md` records Component Model research and migration direction.
- `docs/design/plugin-packages.md` records package/runtime metadata direction.

Concrete implementation work remains tracked by implementation Tickets such as package discovery, Tool registration, WASM runtime, permission grants, CLI inspection, `https`, `fs`, and Component Model runtime migration. Future Plugin work should be filed as concrete implementation Tickets, not broad design umbrella Tickets.