adding more nodes

docs/nodes/Grain Summary.md

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+# Grain Summary
+
+Compute aggregate statistics for all grains in a mask: count, density, coverage fraction, mean/median area, total volume, and height statistics. Equivalent to Gwyddion's grain_summary.c module.
+
+## Inputs
+
+| Name | Type | Required | Description |
+|------|------|----------|-------------|
+| field | DATA_FIELD | Yes | Input surface data |
+| mask | IMAGE | Yes | Binary mask defining grain regions |
+
+## Outputs
+
+| Name | Type | Description |
+|------|------|-------------|
+| summary | RECORD_TABLE | Table of aggregate grain statistics |
+
+## Controls
+
+| Name | Type | Default | Description |
+|------|------|---------|-------------|
+| min_size | INT | 10 | Minimum grain size in pixels to include (1–100000) |
+
+## Notes
+
+- Reported statistics: grain count, grain density (count per unit area), coverage fraction, mean area, median area, total volume, mean height, median height, max area, min area.
+- Volume is computed relative to the mean height of the non-grain background.
+- Use Grain Analysis for per-grain statistics, or Grain Distributions for histograms.