fix(cursor): make GitHub marketplace imports indexable

[zzAllenn]

Summary

• package the Cursor marketplace entry from the repository-local plugins/agentkey directory so GitHub marketplace imports can index AgentKey
• generate the nested Cursor manifest and Skill bundle from the canonical root files
• run the generator in CI and fail with a repair command when committed generated files are stale
• document the generated-directory contract and Cursor refresh behavior in both English and Chinese

Why

Cursor's marketplace indexer expects a local marketplace source to resolve to a self-contained plugin directory. The previous root source could work when loaded from a local checkout but GitHub imports indexed zero plugins. The repository-local package fixes that boundary, while the generator and CI guard prevent its duplicated distribution files from becoming a second source of truth.

Developer impact

Maintainers edit only .cursor-plugin/plugin.json and skills/agentkey/. plugins/agentkey/ is generated by ./scripts/sync-cursor-marketplace-plugin.sh; CI runs the generator on Linux and macOS and rejects any uncommitted generated diff. CI intentionally does not auto-commit to contributor branches.

Validation

• npx -y bats tests/ — 26/26 passed
• npx -y bats tests/cursor-plugin.bats — 6/6 passed
• bash -n scripts/sync-cursor-marketplace-plugin.sh
• JSON manifest validation with jq
• generator rerun leaves plugins/agentkey/ unchanged
• git diff --check origin/main...HEAD