Adds --all to /gsd-discuss-phase so users can skip the AskUserQuestion area-selection step and jump straight into discussing all gray areas interactively. Unlike --auto, --all does NOT auto-advance to plan-phase — it only eliminates the selection friction while keeping full interactive control over each discussion. Closes #2188 Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>