Fix #7770, #7747, #7572, #7522, #7416, #7086: Bug when first point in poly tool clicked twice

Previous logic always skipped the first point. Instead, it should only
skip when actually closing a loop (i.e. >= 3 points).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/bonsai/bonsai/tool/polyline.py

@@ -533,9 +533,12 @@ class Polyline(bonsai.core.tool.Polyline):
             polyline_data = polyline_data[0]
         polyline_points = polyline_data.polyline_points
         if polyline_points:
-            # Avoids creating two points at the same location
-            for point in polyline_points[1:]:  # The first can be repeated to form a wall loop
+            # Avoids creating two points at the same location.
+            # The only exception is repeating the first point to close a loop (requires >= 3 existing points).
+            for i, point in enumerate(polyline_points):
                 if (x, y, z) == (point.x, point.y, point.z):
+                    if i == 0 and len(polyline_points) >= 3:
+                        continue
                     return "Cannot create two points at the same location"
             # Avoids creating overlapping edges
             if len(polyline_points) > 1: