feat(qw2): hook LoopDetector dans api_stream + extension replay_state

replay_state enrichi de _screenshot_history (5 dernières images PIL) et
_action_history (5 dernières signatures action).

report_action_result :
- met à jour les deux anneaux après chaque action
- évalue le LoopDetector (singleton lazy avec _clip_embedder serveur)
- si detected → bascule paused_need_help avec pause_reason="loop_detected"
  et bus event lea:loop_detected (signal + evidence)

Tous les chemins d'erreur (embedder absent, OOM, exception) loggent et
laissent le replay continuer — aucun blocage par la couche détection.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

agent_v0/server_v1/api_stream.py

@@ -3942,6 +3942,82 @@ async def report_action_result(report: ReplayResultReport):
                 f"— worker VLM autorisé à reprendre"
             )
 
+        # ===================================================================
+        # QW2 — LoopDetector : alimentation des anneaux + évaluation
+        # ===================================================================
+        # On n'évalue que si le replay est encore "running" — inutile de
+        # pauser quelque chose de déjà completed/error/paused.
+        if replay_state["status"] == "running":
+            # Snapshot image (PIL) dans l'anneau
+            try:
+                from PIL import Image
+                ss_raw = screenshot_after or replay_state.get("last_screenshot")
+                img = None
+                if isinstance(ss_raw, str) and ss_raw:
+                    if os.path.isfile(ss_raw):
+                        img = Image.open(ss_raw).copy()  # détache du file handle
+                    else:
+                        # Possible base64 — décoder
+                        try:
+                            import base64
+                            import io as _io
+                            img_bytes = base64.b64decode(ss_raw, validate=False)
+                            img = Image.open(_io.BytesIO(img_bytes)).copy()
+                        except Exception:
+                            img = None
+                if img is not None:
+                    replay_state.setdefault("_screenshot_history", []).append(img)
+                    replay_state["_screenshot_history"] = replay_state["_screenshot_history"][-5:]
+            except Exception as e:
+                logger.debug("LoopDetector: snapshot historique échoué: %s", e)
+
+            # Snapshot signature de l'action courante
+            try:
+                _act_pos = report.actual_position or {}
+                action_sig = {
+                    "type": (original_action or {}).get("type")
+                            or replay_state.get("_last_action_type", ""),
+                    "x_pct": _act_pos.get("x_pct") if isinstance(_act_pos, dict)
+                             else (original_action or {}).get("x_pct"),
+                    "y_pct": _act_pos.get("y_pct") if isinstance(_act_pos, dict)
+                             else (original_action or {}).get("y_pct"),
+                }
+                replay_state.setdefault("_action_history", []).append(action_sig)
+                replay_state["_action_history"] = replay_state["_action_history"][-5:]
+            except Exception as e:
+                logger.debug("LoopDetector: snapshot action_sig échoué: %s", e)
+
+            # Évaluation (silencieux si rien)
+            try:
+                verdict = _get_loop_detector().evaluate(
+                    replay_state,
+                    screenshots=replay_state.get("_screenshot_history", []),
+                    actions=replay_state.get("_action_history", []),
+                )
+                if verdict.detected:
+                    replay_state["status"] = "paused_need_help"
+                    replay_state["pause_reason"] = "loop_detected"
+                    replay_state["pause_message"] = (
+                        f"Léa semble bloquée — {verdict.signal} "
+                        f"(détail: {verdict.evidence})"
+                    )
+                    logger.warning(
+                        "LoopDetector: replay %s mis en pause — signal=%s evidence=%s",
+                        replay_state["replay_id"], verdict.signal, verdict.evidence,
+                    )
+                    # Bus event d'observabilité (logger pattern QW1)
+                    try:
+                        logger.info(
+                            "[BUS] lea:loop_detected replay=%s signal=%s evidence=%s",
+                            replay_state["replay_id"],
+                            verdict.signal,
+                            verdict.evidence,
+                        )
+                    except Exception as _e_bus:
+                        logger.debug("emit lea:loop_detected échec: %s", _e_bus)
+            except Exception as e:
+                logger.warning("LoopDetector: évaluation échouée (non bloquant): %s", e)
+
     return {
         "status": "recorded",
         "action_id": action_id,