Enforces the rails the vault depends on: only directories are linked
(agent editing tools refuse to write through a symlinked file), a missing
target is refused rather than turned into a dangling link, and adopting a
populated live directory copies without clobbering.
Also fixes slug sanitization in _agents_repo_slug to apply the same
[^a-z0-9._-] → - mapping to the fallback (no-remote) branch, ensuring
local project slugs are filesystem-safe and won't leak special chars like
spaces or exclamation marks.
rootiest
3fd9476fbc