Build VersionedLayoutConfig from flags+config with dotenv expansion.
Expansion policy:
dotenvExpand
interpolateDeep
{ ...process.env, ...ref }
CLI flags relevant to layout.
Optional
Plugin config slice (already interpolated by host).
Env reference (typically ctx.dotenv).
VersionedLayoutConfig for path/token resolution.
Build VersionedLayoutConfig from flags+config with dotenv expansion.
Expansion policy:
dotenvExpand/interpolateDeep.{ ...process.env, ...ref }(ctx wins).