/branch — isolated worktree for parallel agent sessions

Two sessions in one working dir race on HEAD (git checkout switches it for everyone), uncommitted edits (leak across checkouts), and the index. Worktrees give each session its own working files, HEAD, and index while sharing .git. This wraps git worktree add with project conventions + a journal entry. Cost: one directory, ~zero git overhead.

Argument shapes

/branch <task-slug> [--from <base-branch>] [--description "<text>"] [--reuse]
/branch list
/branch done <task-slug> [--force]
/branch update [--working-on "..."] [--state <state>] [--next "..."] [--blocked-by "..."] [--asks "..."] [--dont-touch "..."] [--slug <slug>]
/branch coord <message>
/branch coord clear <slug>

Parse the first positional arg and dispatch: list→list mode, done→done mode, update→update mode (heartbeat current entry), coord→coord mode (manage ## Coordination), anything else→create mode (treat the arg as a task slug).