With Config.Wing a source goes to wiki/<wing>/sources/ (wing/hall frontmatter);
concepts and entities stay in the shared wiki/concepts and wiki/entities, so an
entity cited from two wings is ONE page with both sources (the per-wing facts/
layout duplicated it). A source slug already used anywhere but its own wing's
sources/ is refused (slug is the graph identity). wiki.FindSlug added.
Mutation-checked: collision guard, shared inventory, per-wing source path.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
Sources -> wiki/<wing>/sources, concepts/entities -> wiki/<wing>/facts with
kind: frontmatter; inventory, title resolution and back-references are
confined to the target wing. Empty Wing keeps the retired layout unchanged.
Mutation-checked: widening the inventory beyond the wing fails the
cross-wing back-reference test; a non-plain wing name is rejected.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>