A plain shell now gets a silverwood `plain-shell` session record on spawn (no lock), so its name persists workstream-scoped instead of only in client state. Connect is kind-aware — a shell reopens as a fresh login shell, skipping the lock/resume — and a new DELETE session route closes a shell (doctor cannot retire a conversation-less shell). Renames the runtime/wire token shell -> plain-shell. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>