results: clamp the contour legend's range; values above it in an over colour (#191)

results.contour takes range {min?, max?} (or "auto"), kept until the field changes: a
singular peak no longer squeezes the field into the bottom bands. Values above a clamped
maximum go to an extra band drawn in the over colour, split exactly at the clamp; the legend
shows that band up to the true maximum and says it is clamped. The results panel has Legend
max/min (Auto or a value), the MCP show_results tool a range argument, and headless pictures
follow the clamp too.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UhhZMBTviDQxZvwnyP89fo

crates/ui-egui/src/theme.rs

@@ -73,6 +73,8 @@ pub struct Tokens {
     pub contour: [Color32; 5],
     /// Faces with no result at a node.
     pub no_result: Color32,
+    /// Values above a clamped legend's maximum (the same in both themes).
+    pub contour_over: Color32,
     // ---- analysis setup symbols ----
     /// Boundary conditions and rigid walls.
     pub glyph_constraint: Color32,
@@ -159,6 +161,7 @@ impl Tokens {
             ],
             contour: CONTOUR,
             no_result: Color32::from_rgb(0x9a, 0xa0, 0xaa),
+            contour_over: Color32::from_rgb(0x6e, 0x2c, 0x80),
             glyph_constraint: Color32::from_rgb(0x00, 0x8a, 0xa8),
             glyph_load: Color32::from_rgb(0xd0, 0x24, 0x24),
             glyph_interaction: Color32::from_rgb(0x9a, 0x30, 0xc0),