Export the current 3D view as 2D DXF with optional hidden lines (#1449)

Adds File > Export > Current View as DXF: the visible bodies projected from the current camera onto 2D LINE/LWPOLYLINE entities, with hidden edges omitted or dashed.

Co-authored-by: cronos <[email protected]>
Co-Authored-By: Claude Sonnet 5.5 <[email protected]>

docs/features.md

@@ -1,6 +1,6 @@
 # Features
 
-SolidCraft's commands by area, generated by `cargo xtask features` from the command registry (`solidcraft-cli commands`). **376 commands.** Planned (registered, not built yet): 3. Every command runs the same way from the toolbar, a script, `solidcraft-cli exec <id> '<json>'`, the control channel and MCP; parameters are in the [command reference](book/src/reference/commands.md) (`cargo xtask book`). Status and plans: [ROADMAP](../ROADMAP.md).
+SolidCraft's commands by area, generated by `cargo xtask features` from the command registry (`solidcraft-cli commands`). **377 commands.** Planned (registered, not built yet): 3. Every command runs the same way from the toolbar, a script, `solidcraft-cli exec <id> '<json>'`, the control channel and MCP; parameters are in the [command reference](book/src/reference/commands.md) (`cargo xtask book`). Status and plans: [ROADMAP](../ROADMAP.md).
 
 ## Sketch (102)
 
@@ -323,7 +323,7 @@ SolidCraft's commands by area, generated by `cargo xtask features` from the comm
 | Compare Bodies | `inspect.compare` | – |
 | Section Analysis | `inspect.section` | SOLID › INSPECT |
 
-## Files (8)
+## Files (9)
 
 | Command | Id | Toolbar |
 |---|---|---|
@@ -335,6 +335,7 @@ SolidCraft's commands by area, generated by `cargo xtask features` from the comm
 | Export | `file.export` | – |
 | Save As Mesh | `file.save_mesh` | MESH › MODIFY |
 | Installed Slicers | `file.slicers` | – |
+| Export Current View as DXF | `file.export_view_dxf` | – |
 
 ## Documents (4)
 

docs/view-dxf.md

@@ -0,0 +1,34 @@
+# Export the current view as DXF
+
+Choose **File → Export Current View as DXF…**, choose whether to omit hidden edges or
+export them as dashed lines, then choose **Export DXF…** and a destination. The hidden-edge
+choice is remembered between runs. The Japanese menu is **ファイル → 現在の表示をDXFでエクスポート…**.
+
+The drawing uses the camera when Export is pressed, including roll, the world's up axis
+and perspective. Only shown bodies are exported, at their current component/occurrence
+placements. Hidden bodies neither draw nor hide other bodies. The complete projected
+geometry is exported, including geometry beyond the viewport's edges. Grid, sketches,
+dimensions, selection highlights and other overlays are excluded. Turn off section analysis
+before exporting.
+
+Coordinates are 2D, Z=0, in millimetres. Orthographic views retain 1:1 dimensions in the
+view plane. Perspective views retain foreshortening, projected onto the plane through the
+camera target; they are intended for illustrations rather than dimensioned fabrication.
+Curves and curved silhouettes are approximated with straight segments at a default
+model-space chord tolerance of 0.01 mm. This is not an exact analytic curve export.
+
+The AutoCAD 2000 ASCII DXF contains `VISIBLE` (continuous) and, when requested, `HIDDEN`
+(2 mm dashes / 1 mm gaps) layers. Hidden curves use connected `LWPOLYLINE` entities with
+continuous linetype generation so the pattern does not restart on each chord. The pattern
+is embedded in the file. The polyline flags follow the
+[Autodesk DXF reference](https://help.autodesk.com/cloudhelp/2017/ENU/AutoCAD-DXF/files/GUID-748FC305-F3F2-4F74-825A-61F04D757A50.htm).
+
+Edges are split where another surface occludes them, including partial occlusion by another
+body. Hidden edges are never included in omit mode. Triangle diagonals and smooth seams
+are excluded; curved-body silhouettes are included. Very complex drawings fail with an
+error rather than returning an incomplete export. If geometry crosses the perspective
+camera's eye plane, zoom out before exporting.
+
+Programmatic callers use `file.export_view_dxf` with `camera: Camera`, `hidden: "omit"` or
+`"dashed"`, optional `tolerance` (0.0001–1 mm) and optional `path`. Without `path`, the
+command returns the DXF text. The command does not modify the design or its undo history.