Interactive "Open planning Session" context menu: launches a scoped
MCP-backed Claude CLI session in Windows Terminal, letting the user
brainstorm and Claude break a rough task into concrete child-tasks
under a flat parent-child hierarchy. Includes schema, MCP tool surface,
terminal launch, UI changes, lifecycle, testing, and a three-plan
phasing (A foundation, then B worker + C UI in parallel).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>