The Design preference surface_extrude_symmetric_per_side, which gave new
symmetric surface extrudes their distance on each side, is removed with
its Surfaces section, its session field and its labels. A symmetric
surface.extrude given no convention splits the total around the start
plane, as solid.extrude does; timeline.edit and timeline.redefine give a
one-sided extrude made symmetric the same. default_extrude_convention,
which only existed to read the preference, goes too.
An explicit `convention: legacy_per_side` and the marker saved designs
carry are unchanged. A saved preferences file that carries the key loads
as before (the prefs test now covers both removed keys).
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
jyvikoandClaude Opus 5.5
a71450aebd