Why: Downstream repositories need a versioned public manifest for skills, MCP, knowledge, parsers, agents, channels, and pages without forking the base.
Evidence: go test ./... passed after omitzero on empty scope and backend so the golden plugin_manifest stays stable.
Impact: apiVersion 1.0 remains accepted. New provides fields are optional. Scope and backend are omitted when zero.
Refs: docs/proposals/2026-10-01-plugin-contract-v2.md
Co-authored-by: Cursor <cursoragent@cursor.com>
