Parallel Story Implementation

Implement multiple independent planned stories concurrently. The leading words are worktree-first: each story gets its own feature branch and isolated worktree before any write-capable child starts. The parent owns planning, route selection, acceptance, review judgment, and approval; children only edit and verify their assigned worktree.

Input

Accept the planned story or issue references plus an optional requested ship mode:

• --ship pr (default) — open one PR per accepted story and stop for review.
• --ship auto — enable auto-merge only when the caller explicitly requests it.
• --ship merge — merge only when the caller explicitly requests it.

Carry the requested mode into every story contract. Do not let an implementation child choose or execute it.