STEP export: unique ids, plain curves, right revolution senses; seams on split faces

Vendored truck-stepio (writer only): an intersection curve's second surface
was written at the first one's id (duplicate ids for every boolean edge),
and revolved surfaces lost their orientation (the modeling-surface sense was
always true; inverted or mirrored revolutions came out inside out). Export
now writes intersection edges as C1 cubic B-splines through exact points,
so files carry plain 3D curves and no redundant surfaces.

Vendored truck-meshalgo: hinted parameter searches that run off a B-spline's
domain are rejected or clamped (meshing their grid never finished).

STEP import: straight revolution profiles are bounded in the meridian plane
and stop at the axis; loops on revolutions start away from the axis; face
extents include edge end points. Edges between pieces of one split surface
draw as seams.

kernel::step_validate checks a STEP file (duplicate ids, dangling
references, dense numbering); the oracle replay now exports every rebuilt
part, validates it and re-imports it with no warnings and the same volume
(all 32 rebuildable cases pass).

Co-Authored-By: Claude Opus 5.5 <[email protected]>
Claude-Session: https://claude.ai/code/session_01AS5Tn3xieewUSg3uxrMVdL

docs/step-import.md

@@ -12,36 +12,73 @@ Read: manifold solid breps (with voids), faceted breps, shell-based surface mode
 
 Generated by `cargo xtask step-corpus`. Each case is a part exported from Fusion as STEP (AP214; kept locally in `plan/fusion/oracle/`, never committed). SolveCraft opens `part.step` exactly as File → Open does (an Import base feature) and compares with Fusion's own measurements: body count, volume and area (relative tolerance 1e-3) and the number of faces read from the file.
 
-**29 / 29 files pass.**
+**60 / 66 files pass.**
 
 | Case | Result | Bodies | Volume mm³ (got / Fusion) | Area mm² (got / Fusion) | Faces (got / Fusion) | ms | Notes |
 |---|---|---|---|---|---|---|---|
-| 01-box | pass | Box | 24000.000 / 24000.000 | 5200.000 / 5200.000 | 6 / 6 | 2 |  |
-| 02-cylinder | pass | Cylinder | 35339.346 / 35342.917 | 6125.844 / 6126.106 | 3 / 3 | 7 |  |
-| 03-box-through-hole | pass | Box | 45738.489 / 45738.053 | 9327.795 / 9327.788 | 7 / 7 | 4 |  |
-| 04-revolve-vase | pass | Vase | 112487.028 / 112499.479 | 13156.053 / 13156.615 | 5 / 5 | 189 |  |
-| 05-taper-extrude | pass | Frustum | 61814.826 / 61814.826 | 9676.915 / 9676.915 | 6 / 6 | 1 |  |
+| 01-box | pass | Box | 24000.000 / 24000.000 | 5200.000 / 5200.000 | 6 / 6 | 16 |  |
+| 02-cylinder | pass | Cylinder | 35339.346 / 35342.917 | 6125.844 / 6126.106 | 3 / 3 | 37 |  |
+| 03-box-through-hole | pass | Box | 45738.489 / 45738.053 | 9327.795 / 9327.788 | 7 / 7 | 28 |  |
+| 04-revolve-vase | pass | Vase | 112487.028 / 112499.479 | 13156.053 / 13156.615 | 5 / 5 | 371 |  |
+| 05-taper-extrude | pass | Frustum | 61814.826 / 61814.826 | 9676.915 / 9676.915 | 6 / 6 | 19 |  |
 | 06-symmetric-extrude | pass | Block | 30000.000 / 30000.000 | 6200.000 / 6200.000 | 6 / 6 | 1 |  |
-| 07-fillet-all-edges | pass | Box | 23340.395 / 23340.849 | 4726.169 / 4726.265 | 26 / 26 | 18 |  |
-| 08-chamfer | pass | Box | 23730.667 / 23730.667 | 5029.352 / 5029.352 | 10 / 10 | 1 |  |
-| 09-shell | pass | Box | 13632.000 / 13632.000 | 13992.000 / 13992.000 | 11 / 11 | 1 |  |
-| 10-rect-pattern-holes | pass | Plate | 29803.869 / 29803.540 | 14652.467 / 14652.389 | 18 / 18 | 76 |  |
-| 11-circular-pattern-flange | pass | Flange | 66758.484 / 66758.844 | 19320.589 / 19320.795 | 10 / 10 | 50 |  |
-| 12-mirror-feature | pass | Base | 21392.261 / 21392.920 | 6530.917 / 6530.973 | 10 / 10 | 7 |  |
-| 13-combine-join | pass | A | 45547.074 / 45571.680 | 8633.463 / 8634.336 | 9 / 9 | 5 |  |
-| 14-combine-cut | pass | A | 42934.678 / 42931.417 | 9706.604 / 9706.858 | 7 / 7 | 61 |  |
-| 15-combine-intersect | pass | A | 54442.787 / 54454.273 | 7381.985 / 7382.743 | 7 / 7 | 134 |  |
-| 16-sweep | pass | Tube | 2584.167 / 2584.724 | 1779.580 / 1779.698 | 5 / 5 | 304 |  |
-| 17-loft | pass | Loft | 35124.785 / 35125.498 | 6496.433 / 6495.000 | 6 / 6 | 148 |  |
-| 18-hole-features | pass | Plate | 33890.986 / 33890.710 | 8568.685 / 8568.696 | 13 / 13 | 63 |  |
-| 19-l-bracket-constrained | pass | LBracket | 14720.000 / 14720.000 | 5472.000 / 5472.000 | 8 / 8 | 1 |  |
-| 20-slot-constrained | pass | Slot | 2965.374 / 2965.487 | 1774.635 / 1774.690 | 6 / 6 | 17 |  |
+| 07-fillet-all-edges | pass | Box | 23340.395 / 23340.849 | 4726.168 / 4726.265 | 26 / 26 | 63 |  |
+| 08-chamfer | pass | Box | 23730.667 / 23730.667 | 5029.352 / 5029.352 | 10 / 10 | 12 |  |
+| 09-shell | pass | Box | 13632.000 / 13632.000 | 13992.000 / 13992.000 | 11 / 11 | 8 |  |
+| 10-rect-pattern-holes | pass | Plate | 29803.869 / 29803.540 | 14652.467 / 14652.389 | 18 / 18 | 270 |  |
+| 11-circular-pattern-flange | pass | Flange | 66758.484 / 66758.844 | 19320.589 / 19320.795 | 10 / 10 | 90 |  |
+| 12-mirror-feature | pass | Base | 21392.261 / 21392.920 | 6530.917 / 6530.973 | 10 / 10 | 16 |  |
+| 13-combine-join | pass | A | 45547.074 / 45571.680 | 8633.463 / 8634.336 | 9 / 9 | 19 |  |
+| 14-combine-cut | pass | A | 42934.679 / 42931.417 | 9706.604 / 9706.858 | 7 / 7 | 95 |  |
+| 15-combine-intersect | pass | A | 54442.787 / 54454.273 | 7381.985 / 7382.743 | 7 / 7 | 223 |  |
+| 16-sweep | pass | Tube | 2584.167 / 2584.724 | 1779.580 / 1779.698 | 5 / 5 | 430 |  |
+| 17-loft | pass | Loft | 35124.785 / 35125.498 | 6496.433 / 6495.000 | 6 / 6 | 91 |  |
+| 18-hole-features | pass | Plate | 33890.986 / 33890.710 | 8568.685 / 8568.696 | 13 / 13 | 26 |  |
+| 19-l-bracket-constrained | pass | LBracket | 14720.000 / 14720.000 | 5472.000 / 5472.000 | 8 / 8 | 9 |  |
+| 20-slot-constrained | pass | Slot | 2965.374 / 2965.487 | 1774.635 / 1774.690 | 6 / 6 | 4 |  |
 | 21-draft | pass | Box | 54574.737 / 54574.737 | 8781.998 / 8781.998 | 6 / 6 | 1 |  |
-| 22-split-body | pass | Cyl, Cyl (1) | 75380.935 / 75398.224 | 12954.433 / 12955.175 | 6 / 6 | 31 |  |
-| 23-bracket-multifeature | pass | Bracket | 59331.560 / 59331.129 | 18290.761 / 18290.737 | 19 / 19 | 74 |  |
-| 24-user-parameters | pass | Block | 34822.124 / 34821.903 | 8114.167 / 8114.159 | 7 / 7 | 23 |  |
-| 25-sketch-triangle | pass | Triangle | 4032.155 / 4032.155 | 2274.099 / 2274.099 | 5 / 5 | 1 |  |
-| 26-sketch-belt | pass | Belt | 11326.051 / 11326.170 | 5637.346 / 5637.404 | 7 / 7 | 27 |  |
-| 27-sketch-trapezoid | pass | Trapezoid | 5342.311 / 5342.257 | 3066.959 / 3066.946 | 8 / 8 | 23 |  |
-| 28-blind-pocket-fillets | pass | Block | 84299.400 / 84299.249 | 16279.542 / 16279.572 | 23 / 23 | 72 |  |
-| 29-two-sided-and-partial-revolve | pass | Block | 25731.359 / 25731.307 | 6312.589 / 6312.602 | 12 / 12 | 14 |  |
+| 22-split-body | pass | Cyl, Cyl (1) | 75380.935 / 75398.224 | 12954.433 / 12955.175 | 6 / 6 | 19 |  |
+| 23-bracket-multifeature | pass | Bracket | 59331.560 / 59331.129 | 18290.761 / 18290.737 | 19 / 19 | 37 |  |
+| 24-user-parameters | pass | Block | 34822.124 / 34821.903 | 8114.167 / 8114.159 | 7 / 7 | 4 |  |
+| 25-sketch-triangle | pass | Triangle | 4032.155 / 4032.155 | 2274.099 / 2274.099 | 5 / 5 | 18 |  |
+| 26-sketch-belt | pass | Belt | 11326.051 / 11326.170 | 5637.346 / 5637.404 | 7 / 7 | 24 |  |
+| 27-sketch-trapezoid | pass | Trapezoid | 5342.311 / 5342.257 | 3066.959 / 3066.946 | 8 / 8 | 9 |  |
+| 28-blind-pocket-fillets | pass | Block | 84299.400 / 84299.249 | 16279.542 / 16279.572 | 23 / 23 | 56 |  |
+| 29-two-sided-and-partial-revolve | pass | Block | 25731.359 / 25731.307 | 6312.589 / 6312.602 | 12 / 12 | 9 |  |
+| 30-fillet-after-shell | pass | Box | 21745.919 / 21745.876 | 14968.279 / 14968.332 | 27 / 27 | 82 |  |
+| 31-fillet-l-all-edges | pass | L | 14321.347 / 14321.626 | 5023.960 / 5024.045 | 38 / 38 | 68 |  |
+| 32-boss-plate-fillets | pass | Part | 33590.191 / 33590.350 | 9929.841 / 9929.864 | 10 / 10 | 620 |  |
+| 33-fillet-tangent-chain | pass | Slot | 8236.938 / 8237.122 | 2793.516 / 2793.569 | 14 / 14 | 202 |  |
+| 34-chamfer-then-fillet | pass | Box | 22892.369 / 22892.421 | 4753.674 / 4753.688 | 18 / 18 | 31 |  |
+| 35-fillet-curved-curved | FAIL | Tee | 63090.315 / 63171.443 | 10267.244 / 10269.348 | 6 / 6 | 1602 |  |
+| 36-corner-blend-two-radii | pass | Box | 57799.345 / 57800.240 | 8585.404 / 8585.524 | 18 / 18 | 88 |  |
+| 37-pyramid-apex-blend | FAIL | Pyramid | 15483.389 / 15465.575 | 3972.101 / 3914.581 | 18 / 18 | 786 |  |
+| 38-coincident-cylinders | pass | A | 15706.106 / 15707.963 | 3769.742 / 3769.911 | 3 / 3 | 27 |  |
+| 39-tee-pipe | FAIL | Tee | 24069.177 / 24096.237 | 16706.241 / 16710.048 | 7 / 7 | 64 |  |
+| 40-box-sphere-torus | pass | A | 36287.351 / 36287.433 | 10695.939 / 10696.165 | 10 / 10 | 764 |  |
+| 41-tube-radial-holes | FAIL | Tube | 20070.139 / 20243.981 | 14849.742 / 14873.773 | 22 / 22 | 428 |  |
+| 42-overlapping-patterns | pass | Plate | 38489.045 / 38487.064 | 21687.203 / 21686.603 | 43 / 43 | 469 | solid 'Plate': imported as an open body (the shell is not closed) |
+| 43-cut-splits-body | pass | Bar, Bar (1) | 28000.000 / 28000.000 | 7200.000 / 7200.000 | 12 / 12 | 19 |  |
+| 44-shell-l-bracket | pass | L | 8384.000 / 8384.000 | 8784.000 / 8784.000 | 15 / 15 | 17 |  |
+| 45-shell-boss-plate | pass | Part | 13676.925 / 13676.602 | 14156.500 / 14156.602 | 15 / 15 | 11 |  |
+| 46-shell-two-open-faces | pass | Box | 16044.000 / 16044.000 | 11398.000 / 11398.000 | 10 / 10 | 2 |  |
+| 47-draft-curved-pocket | pass | Block | 111388.144 / 111387.712 | 17700.329 / 17700.361 | 11 / 11 | 11 |  |
+| 48-pulley | pass | Pulley | 168507.117 / 168510.841 | 23718.181 / 23718.644 | 12 / 12 | 83 |  |
+| 49-helical-sweep | pass | Spring | 4736.230 / 4738.099 | 4766.821 / 4767.652 | 3 / 3 | 390482 | solid 'Spring': face wrapping around a closed surface kept whole: split line does not reach the rings |
+| 50-sweep-tight-bend | FAIL | Bend | 3822.321 / 3758.443 | 1708.995 / 2153.937 | 5 / 5 | 1797 |  |
+| 51-loft-rect-circle-offset | pass | Loft | 61143.729 / 61133.116 | 9415.804 / 9411.655 | 6 / 6 | 142 |  |
+| 52-circular-pattern-fillet | pass | Hub | 47206.223 / 47206.850 | 14142.022 / 14142.171 | 21 / 21 | 625 |  |
+| 53-path-pattern | pass | Plate | 35010.589 / 35010.398 | 16463.939 / 16463.894 | 13 / 13 | 87 |  |
+| 54-mirror-body-fillets | pass | Bracket | 22780.205 / 22780.089 | 6972.823 / 6972.832 | 12 / 12 | 38 |  |
+| 55-tapped-hole-cosmetic | pass | Plate | 17542.404 / 17542.314 | 4761.584 / 4761.596 | 8 / 8 | 13 |  |
+| 56-holes-on-curved-face | FAIL | Cyl | 77733.175 / 77942.388 | 10590.123 / 10593.139 | 7 / 7 | 93 |  |
+| 57-hole-pattern-sketch-points | pass | Plate | 36767.098 / 36766.712 | 11818.159 / 11818.153 | 24 / 24 | 165 |  |
+| 58-phone-stand | pass | Stand | 74559.445 / 74559.177 | 29148.741 / 29148.785 | 19 / 19 | 25 |  |
+| 59-enclosure-base | pass | Enclosure | 34309.026 / 34309.486 | 33795.404 / 33795.610 | 39 / 39 | 74 |  |
+| 60-pipe-flange | pass | Flange | 323660.116 / 323660.979 | 56984.492 / 56984.564 | 16 / 16 | 495 |  |
+| 61-shaft-keyway | pass | Shaft | 47493.351 / 47525.946 | 9675.779 / 9677.096 | 14 / 14 | 77 |  |
+| 62-heat-sink | pass | HeatSink | 43125.000 / 43125.000 | 45725.000 / 45725.000 | 66 / 66 | 41 |  |
+| 63-hinge-knuckle | pass | Hinge | 4781.312 / 4783.117 | 4109.841 / 4110.287 | 14 / 14 | 47 |  |
+| 64-sketch-tangent-arc-chain | pass | Wave | 4800.000 / 4800.000 | 3843.701 / 3843.712 | 9 / 9 | 47 |  |
+| 65-sketch-gear-tooth | pass | Tooth | 3987.829 / 3988.084 | 1945.416 / 1945.485 | 9 / 9 | 20 |  |
+| 66-sketch-linkage | pass | Link | 8045.431 / 8045.386 | 4308.168 / 4308.175 | 10 / 10 | 94 |  |