fix(workflow): consistent phase transition routing through discuss-phase (#530)

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>

get-shit-done/workflows/discuss-phase.md

@@ -252,6 +252,7 @@ Ask 4 questions per area before offering to continue or move on. Each answer oft
 
    If "More questions" → ask 4 more, then check again
    If "Next area" → proceed to next selected area
+   If "Other" (free text) → interpret intent: continuation phrases ("chat more", "keep going", "yes", "more") map to "More questions"; advancement phrases ("done", "move on", "next", "skip") map to "Next area". If ambiguous, ask: "Continue with more questions about [area], or move to the next area?"
 
 4. **After all areas complete:**
    - header: "Done"