M4.93: DXF drawings open and place with layout, scale or fit, centring and merged layers

ASCII DXF of any version opens (document.open) and places (file.place) through
a new reader in vectorcraft-cad: lines, LW/2D/3D polylines with bulge arcs,
circles, arcs, ellipses, NURBS splines (exact Beziers up to cubic, fitted
otherwise), solids, solid and pattern hatches, TEXT/MTEXT/ATTRIB as point
type, named blocks as symbols (one per look for by-block art), anonymous
blocks and dimensions as groups, MINSERT arrays, OCS extrusion; layers keep
off/frozen/locked/plot state; ACI and true colour, lineweights, linetypes and
transparency resolve through layers and blocks. The `dxf` option object picks
the layout, ratio or fit, lineweight scaling, centring and merged layers;
document.dxfInfo lists layouts, layers and units. Binary DXF and DWG answer a
clear error. The DXF Import Options dialog (dxfImport) asks on open and place
with a layout preview. Fuzzed in import_fuzz.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

docs/control-protocol.md

@@ -307,6 +307,15 @@ Export Selected Art Only with nothing selected, keeps the dialog open), remember
 writes the file (asking for a path when there is none). Export As also lists DWG, greyed out: setting its `format` to
 `dwg` shows, and on confirm answers, the hint to export DXF instead.
 
+DXF Import Options: opening a DXF drawing through the app (`app.open`, `file.open`, a drop) or placing one
+(`file.place` with a `.dxf` file and no `dxf` options, which answers `{"dialog": "dxfImport"}`) opens the `dxfImport`
+dialog (`mode`: `open` or `place`; `layouts`, `units` and `version` describe the drawing). Its fields are the
+`document.open` `dxf` options: `layout` (one of `layouts`), `fit`, `unit` (a unit name such as `Millimeters`) and
+`scale` (1 unit = `scale` drawing units; ignored with `fit`), `scaleLineweights`, `center`, `mergeLayers`.
+`ui.dialog.confirm` opens or places the drawing (placing keeps the other `file.place` params in `__place`) and
+remembers `fit`, `scaleLineweights`, `center` and `mergeLayers` for the next drawing; an error (an unknown layout,
+art too large at that scale) keeps the dialog open.
+
 Placement Options: the Links panel's flyout (or `ui.placementOptionsDialog {ids?}` for agents) opens the
 `placementOptions` dialog for the selected images (fields `ids`, `preserve`: `transforms`/`bounds`/`fileDimensions`/
 `fit`/`fill`, `align`: `topLeft` … `bottomRight`, `clip`). `ui.dialog.confirm` runs `links.placementOptions` with them as

docs/mcp.md

@@ -1112,6 +1112,30 @@ opened.
 {"name":"export","arguments":{"path":"/tmp/plan.dxf","options":{"useArtboards":true,"colors":256}}}
 ```
 
+## DXF import
+
+`document.open` reads ASCII DXF drawings of any version (by content or the `.dxf` extension), and `file.place`
+places one as a group. Both take `dxf: {layout, unit, scale, fit, fitTo, scaleLineweights, center, mergeLayers}`
+(all optional). `document.dxfInfo` reads a drawing without opening it: its `version`, drawing `units`, `layouts`
+(`Model` first, then the paper layouts), `layers`, and the default ratio (`unit`, `scale`: the drawing at 1:1 in its
+own unit; unitless metric drawings read millimetres, imperial ones inches). A ratio is 1 `unit` of the art = `scale`
+drawing units; `fit: true` instead scales the art to fit `fitTo` (a letter page when opening; when placing, the
+artboard under `at`). `center: false` puts the drawing's origin (fitted art: its bottom-left corner) on the
+artboard's bottom-left corner; `mergeLayers` puts all art on one layer. Each DXF layer holding art becomes a layer
+(off and frozen layers hidden, locked ones locked, non-plotting ones non-printing). Lines, polylines (arc segments from
+bulges), circles, arcs, ellipses, splines (NURBS, within a millionth of their size), solids and hatches become paths (solid
+hatches filled, pattern hatches as their boundaries), text and multiline text point type, named blocks symbols
+(one per look when their art takes colour "by block"), anonymous blocks such as dimensions groups. Indexed colours
+(7 is black on paper), true colour, lineweights (`scaleLineweights` scales them with the art), linetypes and
+transparency resolve through layers and blocks. What is left out (viewports, images, meshes, unknown entities) is
+listed in `warnings`. Binary DXF and DWG files answer an error saying to save them as ASCII DXF.
+
+```json
+{"name":"run_command","arguments":{"command":"document.dxfInfo","params":{"path":"/tmp/plan.dxf"}}}
+{"name":"run_command","arguments":{"command":"document.open","params":{"path":"/tmp/plan.dxf","dxf":{"layout":"Layout1","fit":true,"mergeLayers":true}}}}
+{"name":"run_command","arguments":{"command":"file.place","params":{"path":"/tmp/detail.dxf","dxf":{"unit":"mm","scale":10,"center":false}}}}
+```
+
 ## Links panel
 
 `links.list {show?: all|missing|modified|embedded, sort?: name|kind|status}` lists every image in the layers, top