The control room for the days when more than one agent session is running — a Sandcastle
run in one pane, an interactive Claude Code session in another, each
with a state badge instead of a scrollback to read. herdr in a project directory attaches
to a background session; detach or close the terminal and the agents keep going. The
liveness signal this repository records for Sandcastle (worktrees, not logs) is the same
problem Herdr solves at the terminal: knowing whether an agent is working or waiting
without watching it.