M0: workspace, geometry foundation, sketch constraint solver, kernel boundary

Co-Authored-By: Claude Opus 5.5 <[email protected]>

crates/engine/Cargo.toml

@@ -0,0 +1,8 @@
+[package]
+name = "solvecraft-engine"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+
+[lints]
+workspace = true

crates/engine/src/lib.rs

@@ -0,0 +1 @@
+