Chart theming: custom named themes + Theme Builder

docs/ux-second-pass.md

@@ -17,6 +17,20 @@ record the resolution into the contract (`docs/architecture/09`+`10` and the rel
   showcase) or settings-cluster placement (a persistent global pref); should the popover
   registry learn nesting; 16 flat options — group presets under a heading?
 
+- **"Edit themes…" action row inside the value picker** (`LivePreview.tsx` —
+  ChartThemeControl). A non-value action lives inside a single-select disclosure (the
+  VS Code theme-picker pattern), placed after the custom-themes block and before the
+  preset roster (first-use feedback: at the very bottom it was invisible without
+  scrolling). Council questions: should an action be visually separated from the
+  values (divider, distinct styling); is a mid-list row that opens a modal instead of
+  selecting surprising to AT users?
+
+- **Theme Builder config editor is a plain textarea** (`ThemeBuilderModal.tsx`). Monaco
+  (with the Vega-Lite config schema for completions) would match the main editor but is
+  heavy inside a modal and untested in that mounting. Revisit whether the builder deserves
+  a Monaco instance, and whether the gallery's canvas charts need text alternatives
+  beyond the per-card captions.
+
 ## Deferred (not design debts, revisit on demand)
 
 - **Drag-and-drop field assignment** — chips are click/keyboard-first by design; drag would