hive-core now fetches each agent's config as a forge-hosted flake input
(git+http://<forge>/agent-configs/<n>.git). Add a git credential helper
(git-credential-hive-forge) that reads the live forge-core admin token on
every invocation and authenticates as the forge core user, wired via the
[credential] stanza in hive-core's $HOME/.gitconfig + on the service PATH.
Reading the token file live means zero stale copies and no resync on
rotation; no token ever lands in a flake URL or lock. Mirrors the existing
github.nix credential-helper pattern.
b806aa253e