feat: fillet fit option reduces a radius too large for its edges (#388)

* feat(kernel): typed TooLarge refusal and fillet_max search

Blend refusals caused only by the size (larger than the neighbouring faces,
taller than the walls, longer than the next edge, larger than a corner
radius) now return KernelError::TooLarge, displayed as before. fillet_max
finds the largest radius below a request at which the fillet of the edges
works, to three significant digits, by building candidates; it is an explicit
call (up to 16 fillets), not run on every refusal.

A corner edge that doesn't run square to the edge is now reported as such
instead of as a blend larger than the neighbouring faces.

Refs #293

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TWc1smHYwTSVrVc8SNvS44

* feat: fillet fit option reduces a radius too large for its edges

solid.fillet takes fit: exact (the default, as before: a radius too large
for the geometry around the edges is refused) or reduce: the radius is
reduced to the largest that works for all the picked edges (kernel
fillet_max, three significant digits, every candidate built). The feature
stores the requested radius, so it refits on every evaluation; when it
reduces, the feature's warning says so and the command returns
radius_applied. Pattern copies of the fillet use the same rule. The file
format writes fit only when it is reduce.

The Fillet dialog gets a Radius Fit row (Exact / Reduce to Fit, constant
radius) and, when the preview reduced the radius, an Applied Radius line;
editing the feature keeps the choice.

One radius for all edges for now; per-edge radii and taper follow.

Refs #293

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01TWc1smHYwTSVrVc8SNvS44

---------

Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Co-authored-by: bherbruck <brennen.herbruck@gmail.com>

crates/kernel/src/lib.rs

@@ -66,7 +66,7 @@ mod thread_tests;
 mod topo;
 mod tspline;
 
-pub use blend::{ChamferSide, chamfer, chamfer_sides, fillet};
+pub use blend::{ChamferSide, chamfer, chamfer_sides, fillet, fillet_max};
 pub use blend_corner::fillet_radii;
 pub use blend_variable::{fillet_chord, fillet_variable, fillet_variable_points};
 pub use body::{Body, CapSignature, EdgeInfo, FaceInfo, FacePaint, FaceSource, Paint};
@@ -105,6 +105,10 @@ pub enum KernelError {
     Invalid(String),
     #[error("the operation failed: {0}")]
     Failed(String),
+    /// A blend or other size too large for the geometry around it (a smaller size may work);
+    /// shown like any feature that isn't supported yet.
+    #[error("the operation failed: not supported yet: {0}")]
+    TooLarge(String),
     /// The third-party kernel panicked; the model is unchanged.
     #[error("kernel internal error: {0}")]
     Internal(String),