SMLib: pin 90aabff, a shelled round stays a cylinder and a step wall is ruled as its plane

tangency-labs/smlib#57 on top of 60b1c6a. It fixes the two engine tests the earlier pin broke:
press_pull_on_curved_faces and a_shell_fillet_does_not_follow_a_gone_edge_onto_a_smooth_seam,
with their expectations unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

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 49c6cc428f3d1d4d9b20d9b2bf85377058c1ef016396082f1d7fa17d6f3c9e3b
-aarch64-pc-windows-msvc e675f1f8eccdc8c902fbb300ba6eca0443a73ecf207ab10a5ecdffa411a0b5df
-aarch64-unknown-linux-gnu 042f9c6af6053673e3ffd20c9791034a66748538a72b88f3bc08ba17eeca103a
-i686-pc-windows-msvc 53fcb55669647484b70e707298e927b70b24301078f3181aa0544854dbcbfe86
-wasm32-unknown-unknown ef5a257974f2ff24c3420fdc4357d67a8da7a8b253508f5af7e549f5556c01ea
-x86_64-apple-darwin b06dd703c07a0527623f77a70bfc421f580a278d5a18fd5828358b6803098dbe
-x86_64-pc-windows-msvc 9a572adf26454401273f9c0d509956c684dd8f9eb8c389846ded36b9fabcdf0f
-x86_64-unknown-linux-gnu 8eda2121cb7f3c50a6d6865c0daae8ed81a910e8cf3e5c5008bc3ffb60d2cf81
+aarch64-apple-darwin 0288998e1d7e0bc14149f7abc2cd7e44852a66af43b187a700981cffdfbc89dc
+aarch64-pc-windows-msvc 51992eb16f529c0969a22d9c852c65c582dd48a8ca5febf28a5f28186dbec000
+aarch64-unknown-linux-gnu 9d0b96bbaf7ae255c0bcd8828fb3cbb0b3ffda053de47bca73edf8429efcffad
+i686-pc-windows-msvc 26f130fc69f57bd0aa0552b653dde5120a6526525145f4f1cf91b8c0914de95f
+wasm32-unknown-unknown a5a0b287078e4d1f216e8d78194cbb839fcd65a2ad9cb93b491ee5aa46902f7d
+x86_64-apple-darwin 83768b97779df83aa11319668be3c78dad1d84f21e20ea6d923ff2a7bf352889
+x86_64-pc-windows-msvc 21f688d0d3d4c5d9e1e3cb33fb2991701a1172299d36bb6342238836a11cb85e
+x86_64-unknown-linux-gnu 5c6145e288a3e7cd741d1f3f2b96a5a39016c9ceac950b1e05ae75a5f4cb5f53

crates/smlib/SMLIB_REV

@@ -1 +1 @@
-60b1c6a33da2af524206d20155096f361ae9484c
+90aabff7937853f94ab1ddb9115382844f369793