feat(theme,interfaces): Introduce a global theming system and unify menu/tab interfaces; migrate components to use themeDefaultStyles and update APIs accordingly

ts_web/elements/00group-input/dees-input-wysiwyg/dees-slash-menu.ts

@@ -12,6 +12,7 @@ import '../../dees-icon/dees-icon.js';
 
 import { type ISlashMenuItem } from './wysiwyg.types.js';
 import { WysiwygShortcuts } from './wysiwyg.shortcuts.js';
+import { themeDefaultStyles } from '../../00theme.js';
 
 declare global {
   interface HTMLElementTagNameMap {
@@ -49,8 +50,10 @@ export class DeesSlashMenu extends DeesElement {
   private callback: ((type: string) => void) | null = null;
 
   public static styles = [
+    themeDefaultStyles,
     cssManager.defaultStyles,
     css`
+      /* TODO: Migrate hardcoded values to --dees-* CSS variables */
       :host {
         position: fixed;
         pointer-events: none;