revert(find_model): drop plane filter — pass full SAM21 cluster to Open3DModel

The pre-SAM21 depth filter and post-SAM21 partition_by_plane were
fighting each other and drowning the actual object cluster. Per
operator request, send Open3DModel the raw SAM21 cluster and let
RANSAC handle outliers itself. The accepted/excluded/SAM21 overlays
in the GUI continue to work; excluded is now always empty and
accepted == SAM21 cluster.

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

src/presa_mano/api/grasp_routes.py

@@ -232,26 +232,20 @@ def find_model(req: FindModelReq) -> dict[str, Any]:
     top = dets[0]
     bbox = _bbox_to_roi(top["bbox"])
 
-    # 2. SAM21, with depth pre-filter so the segmentation cannot leak onto
-    #    the table around the object: pixels whose back-projection sits below
-    #    the plane have their depth zeroed BEFORE SAM21 sees them, so they
-    #    never end up in the cloud regardless of the mask outline.
+    # 2. SAM21 — full cluster, no plane filtering at all.
     try:
-        seg = segment_with_sam21(nuwa, sam21, bbox, sw,
-                                 pre_filter_plane=get_work_plane())
+        seg = segment_with_sam21(nuwa, sam21, bbox, sw)
     except Sam21Fallback as e:
         raise HTTPException(status_code=422, detail=f"SAM21 fail: {e}")
 
-    # 3. Partition by plane
-    with sw.step("partition_plane"):
-        accepted_m, excluded_m, plane_info = partition_by_plane(
-            seg.points_cv_m, get_work_plane()
-        )
+    accepted_m = seg.points_cv_m
+    excluded_m = np.empty((0, 3), dtype=np.float64)
+    plane_info = {"plane_applied": False,
+                  "n_points_before_plane": int(accepted_m.shape[0])}
     if accepted_m.shape[0] < 10:
         raise HTTPException(
             status_code=422,
-            detail=f"too few accepted points after plane filter: {accepted_m.shape[0]}"
-                   f" (before plane: {plane_info['n_points_before_plane']})"
+            detail=f"too few SAM21 points: {accepted_m.shape[0]}"
         )
 
     # 4. Open3DModel pose