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/doc/src/document.rs

@@ -328,6 +328,9 @@ pub enum FeatureKind {
         /// radius varying along each edge.
         #[serde(default, skip_serializing_if = "FilletStyle::is_constant")]
         style: FilletStyle,
+        /// What to do when the radius is too large for the geometry around the edges.
+        #[serde(default, skip_serializing_if = "FilletFit::is_exact")]
+        fit: FilletFit,
     },
     Chamfer {
         edges: Vec<Vec3>,
@@ -916,6 +919,22 @@ pub enum FilletStyle {
     },
 }
 
+/// A fillet radius too large for the geometry around its edges: refused (`Exact`, the default),
+/// or reduced to the largest that works for all of them (`Reduce`), with a warning.
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum FilletFit {
+    #[default]
+    Exact,
+    Reduce,
+}
+
+impl FilletFit {
+    pub fn is_exact(&self) -> bool {
+        *self == FilletFit::Exact
+    }
+}
+
 impl FilletStyle {
     pub fn is_constant(&self) -> bool {
         *self == FilletStyle::Constant