kernel, cli: clippy and the cli tests build again

prism.rs's sheet regions import Surface and Vec3 only where they are built (the smlib feature),
so the kernel without it has no unused imports; the cli's tests that measure meshes at their own
tolerance depend on solidcraft-kernel.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017itGh5fpMEousnZ91cYcVt

Cargo.lock

@@ -4253,6 +4253,7 @@ dependencies = [
  "serde_json",
  "solidcraft-engine",
  "solidcraft-gpu",
+ "solidcraft-kernel",
  "solidcraft-mcp",
 ]
 

apps/solidcraft-cli/Cargo.toml

@@ -38,3 +38,5 @@ serde_json = { workspace = true }
 [dev-dependencies]
 # Snapshot tests decode the pictures to compare them with a tolerance.
 image = { workspace = true }
+# Tests measure meshes at their own tolerances.
+solidcraft-kernel = { workspace = true }

crates/kernel/src/prism.rs

@@ -4,8 +4,7 @@
 //! result's boundaries are the operands' curves, cut at their crossings and never refitted.
 //! Also the test of whether a record surface is a wall swept along a direction.
 
-use solidcraft_geom::brep::Surface;
-use solidcraft_geom::{Plane, Region2, Seg2, Vec2, Vec3};
+use solidcraft_geom::{Plane, Region2, Seg2, Vec2};
 
 use crate::body::Body;
 use crate::{BoolOp, KernelError, Result};
@@ -111,6 +110,8 @@ struct Regions {
 
 #[cfg(feature = "smlib")]
 mod sheets {
+    use solidcraft_geom::Vec3;
+    use solidcraft_geom::brep::Surface;
     use solidcraft_geom::Loop2;
     use solidcraft_geom::brep::Loop;
     use solidcraft_smlib::{BooleanOp, Brep};