SMLib: pin 68fb916 (tangency-labs/smlib#67)

The owner's bar running tangent into a cylinder rounds its concave arc and
its top edge both together and one after the other in either order, at
r 1 to 7. Two more peg cases come off the fillets known-failing list.

The ladder's shelled dome ring now has 9 edges, not 7: each of its two
cylinder walls is one full-turn face with its seam edge (one wall face per
extruded circle), where it was two halves. Faces, vertices, area and volume
are unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NvoxKQ2rEZvcXNQnhE3Sgs

crates/smlib/SMLIB_PREBUILT

@@ -1,10 +1,10 @@
 # Rust target, SHA-256 of smlib-<target>.tar.gz in the release prebuilt-<SMLIB_REV> of
 # tangency-labs/smlib. Written by scripts/fetch-smlib.sh --pin; never edited by hand.
-aarch64-apple-darwin a0fe19504aee96d2e5de3ac9e4ef7215d649ebb420373a7cc93d62eca3761e2f
-aarch64-pc-windows-msvc ad359c3996e4255086b193722a987286c1d094556eb053df80fd1538c5f9340d
-aarch64-unknown-linux-gnu 4d0ac76e060de13a67ab60de6b207598bfc79d68b649875caaedbab4cac63d5a
-i686-pc-windows-msvc 1218c4f9fa94f769fe8c45ee29d166d1aecd27cb57486de8883c7fba699f6812
-wasm32-unknown-unknown d61597525a3e1c6910890f9848cb85bb5934b2bcdfd8e6551246d90f8b5f94b8
-x86_64-apple-darwin 395f629a4e88132ae69874ff55898f493df75b4d8627a6a663f92ca6b633eb58
-x86_64-pc-windows-msvc 89876ff51ced8dd0513f3837ea1c12965ff957fec3d10051321da31014d24619
-x86_64-unknown-linux-gnu b4bd2990bd100f9a00a24b77f743208f4395adb8725924bcf939fd04a873ef10
+aarch64-apple-darwin 40e2e07835f7622f7b376e7586f2fd76406e6c8ae4d7d9db0047db9cba26a69d
+aarch64-pc-windows-msvc dd406f2d33186b83f2e0134d1c71fb32e67c36a3dddbceb834161a9a2f5bdb17
+aarch64-unknown-linux-gnu ae66dca5c3687c298997299bbd54ce932ef6ea5223538a23f79784e625751a83
+i686-pc-windows-msvc a03b6d407a5ddc7ec07a94064fde8ae2962f3397da1b4ad2465cef4c8f2720ea
+wasm32-unknown-unknown b62905369f173728f12f252a7d3bd49827e39e2d9bdedfcd54555359508acb5a
+x86_64-apple-darwin 482da759ea62ffc0fbfaaa33eb90496852b5431bd06661465f3ebf2387ee23fa
+x86_64-pc-windows-msvc 12c285085d7fceecd3dd18712ed4cabc717ea3b4db32712ece5958c9a40492ad
+x86_64-unknown-linux-gnu 1ba8094a1a2632c1cc46064e68dfadada2f9ce1c988b80155950de901114b68f

crates/smlib/SMLIB_REV

@@ -1 +1 @@
-f8fd83e2fd5a70cf036fffbfaff0e7bc88e0563a
+68fb91627edfea2c5d9251b949c6f2ef8eb23c56

tests/kernel-cases/fillets/KNOWN_FAILING

@@ -45,5 +45,3 @@ every-hole-top-rim-r12-past-plate-bottom SMLib status 1001: a convex round past
 every-pocket-floor-and-rim-edges-r2 a corner patch where two rim rounds meet at each concave pocket corner (23 faces, not 19) instead of the mitre the rounds make running into each other
 every-pocket-rim-edges-r2 a corner patch where two rim rounds meet at each concave pocket corner (19 faces, not 15) instead of the mitre the rounds make running into each other
 every-pocket-rim-edges-r5-as-deep-as-pocket a corner patch where two rim rounds meet at each concave pocket corner (15 faces, not 11) instead of the mitre the rounds make running into each other
-report-fillet-curvature-three-edges-at-bar-corner SMLib's check refuses the open setback sheet of curvature rounds: a 2D B-spline curve cusp (SmBSplineCurve test 13)
-report-fillet-edge-tangent-at-one-end-into-cylinder SMLib refuses the round as larger than the faces beside its edges allow (SMLIB_ERR_NO_ROOM): it fades to nothing at the edge's tangent end, on the wall SMLib now gets back as its cylinder

tests/kernel-cases/ladder/golden.json

@@ -1672,7 +1672,7 @@
       "measured": {
         "area_mm2": 5332.688157880919,
         "body_count": 1,
-        "edges": 7,
+        "edges": 9,
         "faces": 6,
         "vertices": 7,
         "volume_mm3": 5540.61199574002