add a few more nodes

docs/nodes/Arc Revolve.md

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+# Arc Revolve
+
+Subtract a cylindrical arc background. A circular arc of the given radius is rolled under each row (or column), and the envelope it traces is subtracted as the background.
+
+## Inputs
+
+| Name | Type | Required | Description |
+|------|------|----------|-------------|
+| field | DATA_FIELD | Yes | Input field |
+
+## Outputs
+
+| Name | Type | Description |
+|------|------|-------------|
+| leveled | DATA_FIELD | Field with arc background subtracted |
+| background | DATA_FIELD | The estimated arc background |
+
+## Controls
+
+| Name | Type | Default | Description |
+|------|------|---------|-------------|
+| radius | INT | 20 | Arc radius in pixels (1–1000) |
+| direction | dropdown | horizontal | Direction to apply the arc: horizontal, vertical, or both |
+
+## Notes
+
+- Larger radii produce smoother backgrounds that follow gentle curvature. Smaller radii track finer features.
+- The "both" direction takes the minimum of horizontal and vertical backgrounds.
+- Deep outliers are suppressed before fitting so that scratches or pits do not pull the arc down.