feat(chat): persona decides to buy/walk — auto-finish + tolerance (temper) + resume

The conversation now ENDS when the persona makes a decision (option C), not when the
trainee clicks a button:
- persona_id replies carry {reply, decision(none/buy/walk), mood}; when decision is
  buy/walk the session auto-finishes (won/lost) with a debrief that reveals latent
  details + per-turn 'turning points'.
- personas have a tolerance (1-5, 'temper'): impatient personas walk away fast after
  poor answers (fed via internal.misses on mood<=-1); tough 'wrong text' cases can
  still be won by a strong, gentle response (judge realism).
- trainee 'Finish' button removed; if they leave mid-chat an active session is resumed
  via /chat/resume (continue, not restart). One-shot lock still enforced once decided.
- mock/tests updated: persona deciding buy -> send auto-finishes won.
Rebuilt dist.

backend/app/services/store.py

@@ -44,6 +44,7 @@ def ensure_persona_shape(p: dict[str, Any]) -> dict[str, Any]:
         "opener": p.get("opener", ""),
         "special": p.get("special", ""),       # e.g. "wrong_text" | ""
         "difficulty": p.get("difficulty", 1),  # 1..5
+        "tolerance": p.get("tolerance", 3),    # misses before this persona walks away (temper)
         "notes": p.get("notes", ""),
     }
     # validate