adding more nodes

docs/nodes/Grain Edge.md

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+# Grain Edge
+
+Detect grain boundaries from a binary grain mask. Outputs a mask of pixels at grain/non-grain borders using 4-neighbour connectivity. Width controls the boundary thickness in pixels. Equivalent to Gwyddion's grain_edge.c module.
+
+## Inputs
+
+| Name | Type | Required | Description |
+|------|------|----------|-------------|
+| field | DATA_FIELD | Yes | Input height field (used for dimension reference) |
+| mask | IMAGE | Yes | Binary grain mask (white = grain) |
+
+## Outputs
+
+| Name | Type | Description |
+|------|------|-------------|
+| edge_mask | IMAGE | Binary mask with grain boundary pixels marked |
+
+## Controls
+
+| Name | Type | Default | Description |
+|------|------|---------|-------------|
+| width | INT | 1 | Boundary thickness in pixels; values greater than 1 dilate the edge outward (1–10) |
+
+## Notes
+
+- A grain pixel is on the boundary if at least one of its 4-connected neighbours (up, down, left, right) is not a grain pixel.
+- When width > 1, the boundary is expanded using binary dilation with a square structuring element of size (2*width - 1).
+- Dilation is masked to stay within the original grain region, so boundaries never extend into non-grain areas.
+- The field and mask must have the same pixel dimensions.