Line tool inference like Fusion: parallel or perpendicular to existing lines, on a line's extension and tangent to circles and arcs, shown with a dashed guide and the snap label; placing the point adds the constraint (the existing curve stays, the new line follows)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL

crates/ui-egui/src/tools.rs

@@ -190,6 +190,7 @@ pub fn place(app: &mut SolveApp, p: (Vec2, Option<String>)) {
                 dimension(app, &tool, &curves);
                 // Chain: the next segment starts at this one's end point.
                 if let Some(id) = curves.first() {
+                    crate::inference::commit(app, id, b.0);
                     let last = tool.pts.len() - 1;
                     tool.pts[last].1 = Some(format!("{id}.end"));
                 }