Mark the section-placement change BREAKING in the changelog

The same mesh and wingtip_distance now give different section positions, and
march_edges no longer returns arclen.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: 1-Bort-1

CHANGELOG.md

@@ -8,10 +8,13 @@
 - The Makie `plot!` methods for a `Panel` or a `BodyAerodynamics` return a
   `Vector{Makie.AbstractPlot}` instead of a `Vector{Any}`; for a `BodyAerodynamics`
   drawn as flat panels it is one flat list rather than a list per panel.
-- `obj_to_yaml` and `perpendicular_sections` spread the sections evenly over the span,
-  measured along the quarter-chord line without its chordwise component, instead of
-  over leading-edge arc length, and `wingtip_distance` is that spanwise length. A tip
-  whose leading edge runs aft no longer gathers sections into its last centimetres.
+- BREAKING: `obj_to_yaml` and `perpendicular_sections` spread the sections evenly over
+  the span, measured along the quarter-chord line without its chordwise component,
+  instead of over leading-edge arc length, and `wingtip_distance` is that spanwise
+  length. A tip whose leading edge runs aft no longer gathers sections into its last
+  centimetres. The same mesh and settings give different section positions, so a tuned
+  `wingtip_distance` and any geometry generated from one have to be redone.
+  `march_edges` no longer returns `arclen`.
 
 ### Fixed