Three routing fixes:
- transition.md checks for CONTEXT.md before routing — discuss-phase when
missing, plan-phase when present (matches progress.md behavior)
- execute-phase.md offer_next delegates to transition.md instead of emitting
duplicate "Next Up" blocks
- discuss-phase.md adds explicit handling for "Other" free-text responses
Closes#530
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>