fix: add legacy API compat shims + fix /observe auto-routing

- POST /agentmemory/session/start -> 200 compat shim (was 404)
- POST /agentmemory/session/end -> 200 compat shim
- GET /agentmemory/observations?sessionId -> compat shim reading legacy KV
- POST /agentmemory/observe: auto-detect folderPath+agentId payload and
route to folder_observe() instead of failing with 400
- Fix viewer: loadFolders circular reference via IIFE capture
- Fix viewer: broken if(false) block that swallowed page init

src/routes/observations.py

@@ -43,7 +43,7 @@ def _get_kv():
 
 
 # ---------------------------------------------------------------------------
-# POST /agentmemory/observe  (legacy raw hook endpoint)
+# POST /agentmemory/observe  (legacy raw hook endpoint + auto-compat shim)
 # ---------------------------------------------------------------------------
 
 @observations_bp.route("/agentmemory/observe", methods=["POST"])
@@ -54,6 +54,30 @@ def api_observe():
 
     try:
         body = request.get_json(force=True) or {}
+
+        # Auto-detect folder-based payload: if folderPath + agentId present,
+        # route to folder_observe instead of legacy observe().
+        folder_path = body.get("folderPath")
+        agent_id = body.get("agentId")
+        text = body.get("text") or body.get("content") or ""
+
+        if folder_path and agent_id:
+            # New folder-based model — delegate to folder_observe
+            payload = {
+                "folderPath": folder_path,
+                "agentId": agent_id,
+                "text": text,
+                "timestamp": body.get("timestamp") or _datetime_now_iso(),
+                "type": body.get("type"),
+                "title": body.get("title"),
+                "concepts": body.get("concepts"),
+                "files": body.get("files"),
+                "importance": body.get("importance"),
+            }
+            res = functions.folder_observe(_get_kv(), payload)
+            return jsonify(res), 201
+
+        # Legacy session-based model
         res = functions.observe(_get_kv(), body)
         return jsonify(res), 201
     except Exception as e:
@@ -138,3 +162,66 @@ def api_folder_observations():
         reverse=True,
     )
     return jsonify({"observations": observations, "folderPath": fp, "agentId": aid}), 200
+
+
+# ---------------------------------------------------------------------------
+# POST /agentmemory/session/start  (legacy compat shim → 200 no-op)
+# ---------------------------------------------------------------------------
+
+@observations_bp.route("/agentmemory/session/start", methods=["POST"])
+def api_session_start():
+    """Legacy session/start — clients in the wild still call this.
+    Return a synthetic session ID so callers don't error out.
+    """
+    auth_err = _check_auth()
+    if auth_err:
+        return auth_err
+
+    import uuid
+    body = request.get_json(force=True) or {}
+    session_id = body.get("sessionId") or f"compat_{uuid.uuid4().hex[:16]}"
+    return jsonify({
+        "sessionId": session_id,
+        "status": "active",
+        "message": "Session model migrated to folder-based. Use /agentmemory/agent/observe.",
+    }), 200
+
+
+# ---------------------------------------------------------------------------
+# POST /agentmemory/session/end  (legacy compat shim → 200 no-op)
+# ---------------------------------------------------------------------------
+
+@observations_bp.route("/agentmemory/session/end", methods=["POST"])
+def api_session_end():
+    auth_err = _check_auth()
+    if auth_err:
+        return auth_err
+    return jsonify({"success": True, "message": "Session model is now folder-based."}), 200
+
+
+# ---------------------------------------------------------------------------
+# GET /agentmemory/observations  (legacy compat shim)
+# ---------------------------------------------------------------------------
+
+@observations_bp.route("/agentmemory/observations", methods=["GET"])
+def api_observations_legacy():
+    """Legacy /observations?sessionId=... shim.
+    Reads from legacy KV scope if data exists, otherwise returns empty list.
+    """
+    auth_err = _check_auth()
+    if auth_err:
+        return auth_err
+
+    session_id = request.args.get("sessionId", "")
+    if not session_id:
+        return jsonify({"observations": [], "sessionId": ""}), 200
+
+    try:
+        obs = sorted(
+            _get_kv().list(functions.KV.observations(session_id)),
+            key=lambda x: x.get("timestamp", ""),
+            reverse=True,
+        )
+        return jsonify({"observations": obs, "sessionId": session_id}), 200
+    except Exception as e:
+        return jsonify({"observations": [], "sessionId": session_id, "error": str(e)}), 200