POST /api/sessions/:sessionId/pending/create queues a pending_changes create via queueCreate (WriteGuardError -> 422 with the guard message). RightRail gains a 'New file from pasted text' modal (path + content) wired through api.coder.createPendingFile; sessionId is threaded down from App.tsx. The staged change shows in the CoderPane DiffPanel for explicit apply. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>