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/loopblend.rs

@@ -356,7 +356,7 @@ fn build(
         }
         let p = joint_point(i).ok_or_else(|| unsupported("degenerate loop joint"))?;
         if !crate::blend::extension_fits(f, p, *q, size * 1e-7) {
-            return Err(unsupported("the blend is larger than the neighbouring faces"));
+            return Err(crate::blend::too_large("the blend is larger than the neighbouring faces"));
         }
     }
     // The offset arcs must not turn inside out; an arc of exactly the blend's radius shrinks
@@ -371,12 +371,12 @@ fn build(
                     *x = true;
                 }
             } else if toward && a.dist(c) <= r + tol {
-                return Err(unsupported("the blend is larger than a corner radius"));
+                return Err(crate::blend::too_large("the blend is larger than a corner radius"));
             }
         }
     }
     if collapsed.iter().all(|x| *x) {
-        return Err(unsupported("the blend is larger than a corner radius"));
+        return Err(crate::blend::too_large("the blend is larger than a corner radius"));
     }
     let mut va: Vec<mt::Vertex> = pa.iter().map(|p| builder::vertex(p3(*p))).collect();
     // A collapsed piece starts and ends at one vertex.
@@ -546,7 +546,11 @@ fn build(
                 let along = (from_p3(other.point()) - from_p3(v.point())).dot(target - from_p3(v.point()));
                 let reach = (target - from_p3(v.point())).len2();
                 if along <= reach + tol {
-                    return Err(unsupported(if face_side { "the blend is longer than the next edge" } else { "the blend is taller than the walls" }));
+                    return Err(crate::blend::too_large(if face_side {
+                        "the blend is longer than the next edge"
+                    } else {
+                        "the blend is taller than the walls"
+                    }));
                 }
                 let nb = if face_side { va.get(i) } else { vb.get(i) }.ok_or_else(|| KernelError::Failed("joint".into()))?;
                 let slot = seam_ends.entry(e.id()).or_insert_with(|| (e.absolute_clone(), None, None));
@@ -562,7 +566,7 @@ fn build(
         let a = a.unwrap_or_else(|| e.absolute_front().clone());
         let b = b.unwrap_or_else(|| e.absolute_back().clone());
         if from_p3(a.point()).dist(from_p3(b.point())) < tol * 10.0 {
-            return Err(unsupported("the blend is longer than the next edge"));
+            return Err(crate::blend::too_large("the blend is longer than the next edge"));
         }
         seam_subst.insert(id, builder::line(&a, &b));
     }