Vendor the maj0sted track layout library and link it into the editor

Drop-in copy of C:\Users\maj00r\Projects\maj0sted-master minus its web/
directory - the WASM frontend is not being ported, the editor drives the
same C++ API natively. What is left is plain C++20 with no dependencies:
domain model (niweleta, plan and profile geometry, fitting, parallelism),
project serialization, rail sampling and the editor document.

src/web/ribbon.cpp was missing from the library source list; added, since
without it the ribbon symbols never make it into the archive.

maj0sted/examples/plan_to_svg.cpp

@@ -0,0 +1,58 @@
+// A simple visual check tool: build a niweleta, fit a compound curve with
+// transition curves between the two straights, apply it, and write the plan to
+// an SVG file you can open in a browser.
+//
+// Usage:  plan_to_svg [output.svg]   (default: plan.svg)
+//
+// The reusable pieces are render::sample() (geometry -> polylines) and
+// io::to_svg(). A different GUI would call render::sample() and paint itself.
+
+#include <cstdio>
+#include <fstream>
+#include <string>
+
+#include "maj0sted/io/svg_writer.hpp"
+#include "maj0sted/maj0sted.hpp"
+#include "maj0sted/render/plan_sampler.hpp"
+
+using namespace maj0sted::domain;
+
+int main(int argc, char** argv) {
+    MapProject project;
+
+    // Two straights forming a 90-degree corner.
+    Niweleta niweleta{NiweletaId{1}, "Demo"};
+    const StraightId entry =
+        niweleta.add_straight(CartesianPosition{0.0, 0.0}, CartesianPosition{300.0, 0.0});
+    const StraightId exit = niweleta.add_straight(
+        CartesianPosition{300.0, 0.0}, CartesianPosition{300.0, 300.0},
+        JointContinuity::AzimuthBreak);
+
+    // A compound curve R120 -> R80 with clothoids at the ends and between arcs.
+    const CompoundFitParameters params{
+        .entry = entry,
+        .exit = exit,
+        .entry_transition = Length::from_metres(30.0),
+        .exit_transition = Length::from_metres(30.0),
+        .arcs = {CompoundArc{Radius::from_metres(120.0), Length::from_metres(60.0),
+                             Length::from_metres(25.0)},
+                 CompoundArc{Radius::from_metres(80.0)}}};
+
+    const FitResult fit = FittingService::fit_compound(niweleta, params);
+    niweleta.apply_fit(fit);
+    project.add_niweleta(std::move(niweleta));
+
+    const maj0sted::render::Scene scene = maj0sted::render::sample(project);
+    const std::string svg = maj0sted::io::to_svg(scene);
+
+    const std::string path = (argc > 1) ? argv[1] : "plan.svg";
+    std::ofstream out(path);
+    if (!out) {
+        std::fprintf(stderr, "cannot write %s\n", path.c_str());
+        return 1;
+    }
+    out << svg;
+    std::printf("wrote %s (%zu polylines) — open it in a browser\n", path.c_str(),
+                scene.polylines.size());
+    return 0;
+}