smlib: the quarter-cylinder sheet offset and the half-disc extrude match the C++ kernel on solidcore

offset_sheet_quarter_cylinder (both solidcore tests) and extrude_half_disc_split_arc's
solidcore_matches_the_cpp_kernel pass: solidcore#1495's linear_sweep_arc_is_cylinder (fork
12918e9, now on) sweeps the partial arc to an SmCylinder as the C++ kernel does (solidcore#1477).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MNXLXkZLQ6T7TSi4wswcmk

crates/smlib/src/core/offset_tests.rs

@@ -433,7 +433,7 @@ cases!(
     thicken_plate_symmetric,
     thicken_a_solid,
     offset_sheet_plate,
-    offset_sheet_quarter_cylinder: ignore = "solidcore#1477: the quarter arc sweeps to an SmSurfOfExtrusion, whose offset exports as a spline, where the fork's 12918e9 sweeps an SmCylinder (solidcore#1477)",
+    offset_sheet_quarter_cylinder,
     offset_sheet_a_solid,
     offset_sheet_a_sphere,
     offset_sheet_a_sphere_to_its_centre,

crates/smlib/src/core/sweep_tests.rs

@@ -435,7 +435,7 @@ cases!(
     extrude_circle,
     extrude_circle_in_two_halves,
     extrude_circle_in_two_frames,
-    extrude_half_disc_split_arc[ignore = "solidcore#1477: solidcore sweeps a partial arc to a surface of extrusion (exported as a rational spline), the C++ kernel to a cylinder; a single half arc does the same (fix #1495, behind an UpstreamFixes flag, next pin)"],
+    extrude_half_disc_split_arc,
     extrude_square_drafted_round,
     extrude_square_drafted_curvature,
     extrude_circle_drafted,