sync/status now resolve the work repository from a fallback chain:
--repo flag > --config flag > AGENT_LIB_CONFIG env > user-level config
(XDG / AppData) > admin platform default. --repo works without any
config file; tokens fall back to AGENT_LIB_GIT_TOKEN/AGENT_LIB_GIT_USER
without ever overriding a configured token. A completely empty chain
yields an error listing every searched location, a minimal config
example and the --repo shortcut.
Closes beads: agent-lib-9o8