The descriptor-driven gate must treat a runtime as layout-driven when its scoped
artifactLayout is non-empty (any kind), not only when it has a skills kind —
windsurf's global layout is agents-only and is a legitimate layout-driven runtime.
Preserve the three legacy special-cased paths (opencode/kilo combined path,
claude-local copyWithPathReplacement).
zcode falls into the default package.json+hooks path (not in the CommonJS-mode
exclusion roster), so its install contract is packageJson: true — matching
observed install output. No runtime === 'zcode' branch is added (AC#3): zcode
gets the default by not being excluded.
d6cf377064