CLI, MCP: the raster scale no longer resizes DXF exports

`vectorcraft-cli run/convert --scale` and the MCP export tool's `scale`
are raster pixels per point, but they were passed to every export, and
DXF reads `scale` as drawing units per unit: a 2x PNG next to a DXF
doubled the drawing and left it unitless ($INSUNITS 0). They now go
only to raster formats. DXF's own scale stays reachable through the
format options.

apps/vectorcraft-cli/tests/cli.rs

@@ -58,6 +58,28 @@ fn run_batch_exports() {
     assert_eq!(last["result"]["artboards"][0]["width"], 200.0);
 }
 
+#[test]
+fn scale_sizes_raster_exports_only() {
+    // --scale is pixels per point. DXF has a `scale` of its own (drawing units per mm) that would
+    // resize the drawing and leave its units unset.
+    let svg = tmp("scale.svg");
+    std::fs::write(&svg, r#"<svg xmlns="http://www.w3.org/2000/svg" width="100" height="50"><rect x="10" y="10" width="30" height="20"/></svg>"#)
+        .unwrap();
+    let svg = svg.to_str().unwrap();
+    let (plain, scaled, png) = (tmp("plain.dxf"), tmp("scaled.dxf"), tmp("scaled.png"));
+    let ok = |args: &[&str]| {
+        let out = Command::new(BIN).args(args).output().unwrap();
+        assert!(out.status.success(), "{args:?}: {}", String::from_utf8_lossy(&out.stderr));
+    };
+    ok(&["convert", svg, plain.to_str().unwrap()]);
+    ok(&["convert", svg, scaled.to_str().unwrap(), "--scale", "2"]);
+    assert!(std::fs::read(&scaled).unwrap() == std::fs::read(&plain).unwrap(), "convert --scale 2 changed the DXF");
+    ok(&["run", "--in", svg, "--export", scaled.to_str().unwrap(), "--export", png.to_str().unwrap(), "--scale", "2"]);
+    assert!(std::fs::read(&scaled).unwrap() == std::fs::read(&plain).unwrap(), "run --scale 2 changed the DXF");
+    // 100 pt at scale 2 → 200 px (IHDR width).
+    assert_eq!(std::fs::read(&png).unwrap()[16..20], 200u32.to_be_bytes());
+}
+
 #[test]
 fn run_reports_errors() {
     let out = Command::new(BIN).args(["run", "--cmd", "nope.nothing"]).output().unwrap();