dsh-workflow-worktree

@dsh-external/workflow reserves a seam for worktree isolation but deliberately ships no implementation — its README states that tasks declaring isolation: "worktree" will fail when no adapter is registered. dsh-workflow-worktree is that missing adapter, giving the workflow engine the ability to lock every write-capable agent into its own Git worktree checkout that cannot touch your working tree and survives a crash.

The design commits to one principle above all: never degrade to the shared checkout. If the directory is not a valid Git working tree, or the worktree cannot be created, prepare() rejects outright and the task fails loudly rather than silently running the agent in your tree. Each lane manifest records runId, taskId, worktree path, branch, and base commit so the binding survives a crash. Uncommitted work is never discarded — dirty lanes are retained and marked retained-dirty, and Git itself refuses to remove a dirty worktree. The lane directory is added to .git/info/exclude rather than a tracked .gitignore, keeping git status clean so workflow verification fingerprints stay stable. dispose() is idempotent, safe for the engine to call on task settle, run failure, or explicit stop.

This plugin is not a manual worktree manager — it is built for the workflow engine. If you want to fork a workspace and keep working in it, a manual worktree plugin is the right tool. If you want spawnAgent with isolation: "worktree" to automatically isolate, recover after crashes, and clean up idempotently, this is the adapter. The two coexist without conflict.