feat(theme-studio): palette generator and preview fidelity

Two strands land together because the generated theme-studio.html bundles every source file into one page and can't be split cleanly.

The palette generator is a preview-first panel: palette-generator-core.js plans the palette and palette-generator-ui.js draws it. Generated colors stay inspectable and tunable through the existing selector, and committing one creates a normal base column. It adds source-mode and scheme controls, a configurable accent count, and color names from color-names.json.

For preview fidelity, syntax and UI colors now resolve through the real Emacs inherit chains, so the preview matches how Emacs renders the theme. resolveSyntaxFg pins dec to ty (Emacs has no decorator face) and otherwise follows comment-delimiter to comment, doc to string, property to variable, function-call to function-name. resolveUiAttr walks mode-line-inactive to mode-line and line-number-current-line to line-number. The decorator label now reads "decorator to type" to match the type face Emacs uses for it.

Design recorded in the two theme-studio specs under docs/.

1 files changed, 49 insertions, 4 deletions

diff --git a/scripts/theme-studio/app-core.js b/scripts/theme-studio/app-core.js
index 5da521773..2761031b9 100644
--- a/scripts/theme-studio/app-core.js
+++ b/scripts/theme-studio/app-core.js
@@ -33,6 +33,51 @@ function mergePackagesInto(map,pkgs){if(!pkgs)return;for(const app in pkgs){if(!
 // against an inherit cycle (returns null rather than recursing forever).
 function effResolve(map,app,face,attr,seen){seen=seen||{};const f=map[app]&&map[app][face];if(!f||seen[face])return null;seen[face]=1;if(f[attr])return f[attr];if(f.inherit&&map[app][f.inherit])return effResolve(map,app,f.inherit,attr,seen);return null;}
 
+// Emacs built-in inherit chains for the syntax categories theme studio exposes.
+// An unset category foreground resolves the way the generated theme renders in
+// Emacs: build-theme.el writes no override for an unset face, so Emacs falls back
+// to the face's own :inherit -- comment-delimiter->comment, doc->string,
+// property-name->variable-name, function-call->function-name -- not to the
+// default foreground.
+const SYNTAX_INHERIT={cmd:'cm',doc:'str',prop:'var',fnc:'fnd'};
+
+// Effective foreground for a syntax category, following the Emacs inherit chain.
+// SYNTAX maps category -> face object with an optional `fg`; DEFAULTFG is the
+// theme's default foreground (the chain's floor). `dec` (decorator) is pinned to
+// `ty`: Emacs has no decorator face and renders decorators with
+// font-lock-type-face, so a dec color set in the studio would never reach Emacs.
+function resolveSyntaxFg(cat,syntax,defaultFg){
+  let k=(cat==='dec')?'ty':cat;
+  const seen={};
+  while(k&&!seen[k]){
+    seen[k]=1;
+    const fg=syntax[k]&&syntax[k].fg;
+    if(fg)return fg;
+    k=SYNTAX_INHERIT[k];
+  }
+  return defaultFg;
+}
+
+// Emacs built-in inherit chains for the ui faces whose parent is also a studio ui
+// face, so an unset attribute previews the way Emacs renders it: mode-line-inactive
+// inherits mode-line, line-number-current-line inherits line-number.
+const UI_INHERIT={'mode-line-inactive':'mode-line','line-number-current-line':'line-number'};
+
+// First set value of ATTR ('fg'/'bg') for ui FACE, walking UI_INHERIT; null when
+// nothing up the chain is set. The caller applies its own floor (default fg,
+// ground, or transparent), since that floor differs per attribute and face.
+function resolveUiAttr(face,attr,uimap){
+  let f=face;
+  const seen={};
+  while(f&&!seen[f]){
+    seen[f]=1;
+    const v=uimap[f]&&uimap[f][attr];
+    if(v)return v;
+    f=UI_INHERIT[f];
+  }
+  return null;
+}
+
 // Standard swatch-dropdown option list: a default entry, then the palette. When
 // cur is set but no longer in the palette, surface it as a "(gone)" entry first.
 function optList(cur,palette){const have=cur===''||palette.some(p=>p[0]===cur);return [['','— default —'],...(have?palette:[[cur,'(gone)'],...palette])];}
@@ -93,9 +138,9 @@ function fgSetFor(face,state){
   const syn=((state&&state.syntaxAssignments)||[]).filter(a=>a&&a.hex);
   if(!syn.length)return {set:[],reason:'empty'};
   const byHex=new Map();
-  const add=(hex,label,isRole)=>{const k=hex.toLowerCase(),cur=byHex.get(k);if(!cur)byHex.set(k,{hex:k,label});else if(isRole&&cur.label==='default')cur.label=label;};
-  if(state&&state.defaultFg)add(state.defaultFg,'default',false);
-  for(const a of syn)add(a.hex,a.role||a.hex,true);
+  const add=(hex,label,name,isRole)=>{const k=hex.toLowerCase(),cur=byHex.get(k);if(!cur)byHex.set(k,{hex:k,label,name:name||label});else if(isRole&&cur.label==='default'){cur.label=label;cur.name=name||label;}};
+  if(state&&state.defaultFg)add(state.defaultFg,'default','default',false);
+  for(const a of syn)add(a.hex,a.role||a.hex,a.name||a.role||a.hex,true);
   return {set:[...byHex.values()]};
 }
 
@@ -322,4 +367,4 @@ function spanNeighborHex(cur,palette,ground,dir){
   return null;
 }
 
-export { nameToHex, normalizePkgFace, buildPkgmap, packagesForExport, mergePackagesInto, effResolve, optList, paletteOptionList, spanNeighborHex, slugify, ramp, fgSetFor, floor, lMax, COVERED_FACES, columnsFromPalette, regenColumn, rankByLightness, stepRepointPlan, sortColumns, sortColumnMembers, groundRoleOfEntry, groundColumnMembersFromPalette, clearPalettePlan, deletePaletteColumnPlan, areAllLocked, lockToggleLabel, toggleLockSet };
+export { nameToHex, normalizePkgFace, buildPkgmap, packagesForExport, mergePackagesInto, effResolve, resolveSyntaxFg, resolveUiAttr, optList, paletteOptionList, spanNeighborHex, slugify, ramp, fgSetFor, floor, lMax, COVERED_FACES, columnsFromPalette, regenColumn, rankByLightness, stepRepointPlan, sortColumns, sortColumnMembers, groundRoleOfEntry, groundColumnMembersFromPalette, clearPalettePlan, deletePaletteColumnPlan, areAllLocked, lockToggleLabel, toggleLockSet };