M0: truck-based kernel with local fillets and chamfers, parametric document timeline

The kernel moved from monstertruck to truck: truck's booleans handle blind
holes, pockets and bosses that monstertruck's did not (see the ADR). Fillets
and chamfers on straight convex edges between planar faces are our own exact
local B-rep operation. The document holds parameters with unit-aware
expressions and a timeline that re-evaluates incrementally.

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

crates/doc/src/lib.rs

@@ -1 +1,34 @@
+//! The SolveCraft document: user and model parameters, and a parametric timeline of features
+//! (sketches, extrudes, revolves, fillets, primitives, combines…). Evaluating the timeline with
+//! the kernel produces the model (bodies and solved sketches). Evaluation is incremental: a
+//! feature is recomputed only when it, a parameter it uses, or an earlier feature changed.
+#![deny(clippy::unwrap_used, clippy::expect_used, clippy::panic, clippy::unimplemented, clippy::todo, clippy::unreachable)]
+#![forbid(unsafe_code)]
 
+mod document;
+mod eval;
+pub mod expr;
+
+pub use document::*;
+pub use eval::{FeatureResult, Model, ModelBody, ModelState, SolvedSketch};
+pub use solvecraft_kernel as kernel;
+pub use solvecraft_sketch as sketch;
+
+#[derive(Debug, Clone, PartialEq, thiserror::Error)]
+pub enum DocError {
+    #[error("expression: {0}")]
+    Expr(String),
+    #[error("{0}")]
+    Invalid(String),
+    #[error("unknown {0}")]
+    Unknown(String),
+    #[error(transparent)]
+    Sketch(#[from] solvecraft_sketch::SketchError),
+    #[error(transparent)]
+    Kernel(#[from] solvecraft_kernel::KernelError),
+}
+
+pub type Result<T> = std::result::Result<T, DocError>;
+
+#[cfg(test)]
+mod tests;