(stroke-linecap="round"), matching the on-screen Lyon tessellation.
Summary of Changes
turtle-lib/src/export_svg.rs:
Added .set("stroke-linecap", "round") to SVG <line> elements.
Added .set("stroke-linecap", "round") to partial arc <path> elements.
Extracted SvgExporter::to_svg_document(&TurtleWorld) -> Document to
allow in-memory SVG inspection and testing.
Added unit tests verifying that both lines and arcs export with
stroke-linecap="round".
turtle-lib/src/state.rs:
Added #[allow(clippy::unused_self)] to SvgLog::clear for clean clippy
passes when compiling without the svg feature.