Worktree Retry Cleanup

Trigger

Before re-dispatching a coder for a task that already has a lane (any prior dispatch status).

Protocol

1. Prefer built-in provisioning cleanup. Re-dispatch normally through the standard coder/worktree path. Provisioning pre-cleans stale same-lane worktrees/branches when ownership is safe and the existing lane is clean.
2. If provisioning blocks: Treat the error as signal. Dirty lanes, lanes active in another worktree, and lanes owned by another active session must be surfaced to the user instead of deleted.
3. If manual cleanup is explicitly required: Do the ownership check FIRST. Confirm the lane is not owned by another ACTIVE session: read .swarm/session/state.json and verify no other session's delegationChains reference <session>/<task>. If another active session owns it, STOP.
4. Remove only the specific lane. Target .swarm-worktrees/<session>/<task>, never the session parent. Prefer git worktree remove .swarm-worktrees/<session>/<task> and then git worktree prune.
5. Delete only confirmed stale branches. git branch -d swarm/lane/<session>/<task> is allowed after confirming the branch is not checked out and contains no needed commits. Use force deletion only with explicit human approval.
6. Verify: git branch --list "swarm/lane/<session>/<task>" returns empty before retrying.

Root cause

Stale same-lane worktrees and branches used to require manual cleanup before retry. Provisioning now handles the safe clean/stale cases automatically and fails closed for dirty, active, or cross-session-owned lanes.