Implement M1.5 visual design foundation: tokens, IBM Plex, theme toggle, chart themes

docs/architecture/02-persistence.md

@@ -240,7 +240,7 @@ export interface UserSettings {
   editor: { fontSize: number; theme: string; minimap: boolean; wordWrap: 'on' | 'off';
             lineNumbers: 'on' | 'off'; tabSize: number };
   performance: { renderDebounce: number };
-  ui: { theme: 'light' | 'experimental'; previewFitMode: 'default' | 'width' | 'height' | 'full' };
+  ui: { theme: 'light' | 'dark'; previewFitMode: 'default' | 'width' | 'height' | 'full' };
   formatting: { dateFormat: 'smart' | 'iso' | 'custom'; customDateFormat: string };
 }
 
@@ -256,7 +256,7 @@ const DEFAULTS: UserSettings = {
 };
 
 // NOTE — editor.theme default is 'auto': the editor theme follows the app UI
-// theme (light -> light editor theme, experimental -> dark) via custom Monaco
+// theme (light -> light editor theme, dark -> dark) via custom Monaco
 // themes that match the app chrome, unless the user picks an explicit override.
 // The explicit-override option set (custom themes; whether to include High
 // Contrast or the stock Monaco themes) is still TBD — see spec §07's provisional
@@ -315,6 +315,8 @@ const SORT_DEFAULTS = { sortBy: 'modified' as const, sortOrder: 'desc' as const
 > **Do:** keep a single complete `DEFAULTS` object as the source of truth and merge over it.
 > **Don't:** read individual keys with bespoke `?? fallback` at each call site; one stale default and the shapes drift.
 
+> **Testing:** exercise localStorage adapters against an **injected stub** (`vi.stubGlobal('localStorage', …)`), not the ambient global. Under Node + happy-dom a non-functional Node `localStorage` global shadows happy-dom's, so relying on the ambient one fails with `localStorage.clear is not a function`. Applies to every prefs/settings adapter test (settings-store today; dataset-payload/prefs stores later).
+
 ---
 
 ## 6. Storage Tiers, Budgets & Quota Monitoring