fix(theme-studio): clamp generated palette spans to the bg/fg bounds

Spanning a color generated steps toward pure black and white, so a column could produce colors darker than bg or lighter than fg. I changed regenColumn to ramp the dark side toward the darker ground endpoint and the light side toward the lighter one, bounded by bg and fg. Pure black/white duplicates are still skipped, and callers that pass no ground fall back to the old black/white ramp.

Node tests cover the bounded span and the no-ground fallback. The #counttest gate asserts the regenerated column stays within the bg/fg bounds.

1 files changed, 1 insertions, 1 deletions

diff --git a/scripts/theme-studio/palette-actions.js b/scripts/theme-studio/palette-actions.js
index e65295bc8..4ea8180bc 100644
--- a/scripts/theme-studio/palette-actions.js
+++ b/scripts/theme-studio/palette-actions.js
@@ -218,7 +218,7 @@ function columnCountControl(f){
 // references and leaving removed ones on their now-gone hex. Returns the removed
 // count, or null on a bad base. Shared by the count control and the base edit.
 function regenColumnInPlace(oldHexes,baseHex,baseName,n,columnId){
-  const r=regenColumn(baseHex,n,{});
+  const r=regenColumn(baseHex,n,{ground:{bg:MAP['bg'],fg:MAP['p']}});
   if(r.error){notify('cannot regenerate from '+baseHex,true);return null;}
   const plan=stepRepointPlan(rankByLightness(oldHexes,baseHex),r.members);
   const oldSet=new Set(oldHexes.map(h=>h.toLowerCase()));