add help docs and ?

docs/nodes/Markup.md

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+# Markup
+
+Draw simple vector shapes (lines, rectangles, circles, arrows) over a DATA_FIELD or IMAGE without flattening the raw data. Shapes are drawn interactively in the preview panel.
+
+## Inputs
+
+| Name | Type | Required | Description |
+|------|------|----------|-------------|
+| input | ANNOTATION_SOURCE (DATA_FIELD or IMAGE) | Yes | Background image or field to annotate |
+
+## Outputs
+
+| Name | Type | Description |
+|------|------|-------------|
+| output | ANNOTATION_SOURCE | Input with vector markup overlay attached |
+
+## Controls
+
+| Name | Type | Default | Description |
+|------|------|---------|-------------|
+| shape | dropdown | arrow | Shape type to draw next: line, rectangle, circle, or arrow |
+| stroke_color | STRING (color picker) | #ff0000 | Color for newly drawn shapes |
+| stroke_width | INT | 3 | Line thickness in display pixels for newly drawn shapes (1–64) |
+| clear_shapes | BUTTON | — | Remove all drawn shapes |
+
+## Limitations
+
+- Shapes are stored as fractional coordinates; physical positions depend on field calibration.
+- Individual shape properties (color, width) cannot be changed after drawing; use Clear Shapes to start over.