fix(work_plane): /fit returns full-scene cloud, not just ROI

The 3D viewer was only seeing points inside the ROI rectangle used for
the plane fit. Now /fit also fetches nuwa.pointcloud (step=4, full frame),
flips to CV frame, and returns it as points_camera (downsampled to
max_preview_points). The user sees the entire scene with red = excluded
by the below-plane filter, cyan = kept.

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

src/presa_mano/api/work_plane_routes.py

@@ -1,6 +1,7 @@
 """Work-plane calibration endpoints: fit (preview), save, get, delete."""
 from __future__ import annotations
 
+import logging
 import time
 from dataclasses import asdict
 from typing import Any
@@ -10,6 +11,8 @@ from fastapi import APIRouter, HTTPException
 from pydantic import BaseModel, Field
 
 from ..perception import filter_outliers, nuwa_to_cv_frame
+
+log = logging.getLogger(__name__)
 from ..perception.work_plane import (
     WorkPlane,
     WorkPlaneError,
@@ -83,17 +86,24 @@ def fit(req: FitReq) -> dict[str, Any]:
         created_at=time.time(),
     )
 
-    # Downsample for preview.
-    if len(pts_cv) > req.max_preview_points:
-        idx = np.random.choice(len(pts_cv), req.max_preview_points, replace=False)
-        preview = pts_cv[idx]
-    else:
-        preview = pts_cv
+    # Fetch the FULL-frame point cloud so the user can see the whole scene in
+    # 3D (not just the ROI), with each point colored by signed distance to
+    # the fitted plane.
+    try:
+        with sw.step("pointcloud_full"):
+            pc_full, _ = nuwa.pointcloud_with_meta(step=4, max_depth_mm=4000)
+    except Exception as e:
+        log.warning("Nuwa full pointcloud failed: %s — falling back to ROI cloud", e)
+        pc_full = pc
+    scene_cv = nuwa_to_cv_frame(pc_full[:, :3]) if len(pc_full) else np.empty((0, 3))
+    if len(scene_cv) > req.max_preview_points:
+        idx = np.random.choice(len(scene_cv), req.max_preview_points, replace=False)
+        scene_cv = scene_cv[idx]
 
     return {
         "plane": asdict(wp),
         "preview": True,
-        "points_camera": preview.tolist(),
+        "points_camera": scene_cv.tolist(),
         "timings_ms": sw.as_dict(),
     }