fix(inpaint): Stitch feathers the whole crop when there is no mask edge

Wiring an Image Crop (no mask) into Inpaint Stitch gave crop_info an all-zeros
mask; in mask blend-mode that resolved to alpha=0 and _blur_alpha pasted
NOTHING (result == original, inpaint lost). An all-ones mask gave a hard
rectangle. stitch_back now detects an all-zeros/all-ones resolved alpha (no
edge to soften) and falls back to the rectangle feather over the full crop, so
the edited crop is pasted with a soft seam and Softness still works. Also
covers a whole-image inpaint with nothing painted.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

nodes/_inpaint_helpers.py

@@ -536,7 +536,18 @@ def stitch_back(crop_info, image, mask, blend, blend_mode, color_match):
     if blend_mode == "whole_crop":
         a = _feather_alpha(a.clamp(0, 1), blend)
     else:
-        a = _blur_alpha(a.clamp(0, 1), blend)
+        ac = a.clamp(0, 1)
+        ab = ac > 0.5
+        if not bool(ab.any()) or bool(ab.all()):
+            # No mask EDGE to soften - an Image Crop crop_info with no per-pixel mask
+            # (all-zeros), an all-ones mask, or a whole-image inpaint with nothing
+            # painted. _blur_alpha would return zeros (paste NOTHING - the inpaint is
+            # lost) or ones (a hard rectangle seam). Fall back to the rectangle feather
+            # over the full crop, so the edited crop IS pasted with a soft seam and the
+            # Softness slider still works for the Image Crop interop.
+            a = _feather_alpha(torch.ones((ch, cw), dtype=torch.float32), blend)
+        else:
+            a = _blur_alpha(ac, blend)
 
     out = base.clone()
     B = int(out.shape[0])