global tooltip system, migrate all title attrs to data-tip/data-help

New tooltip.js module with styled tooltips (data-tip) and multi-line
inline help (data-help). Migrates all ~70 native title attributes
across index.php, JS modules, and all plugins. Adds inline help on
9 strategic UI elements (split, superview, zen, extract, assets, etc).

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

public/js/app.js

@@ -13,6 +13,7 @@ import { openModal, closeModal, saveCard, saveOnly, openFindBar } from './module
 import { openSearch, closeSearch } from './modules/search.js';
 import { showContextMenu } from './modules/context-menu.js';
 import { undo, canUndo } from './modules/undo.js';
+import './modules/tooltip.js';
 import { registerShortcut, guards, renderShortcutHelp } from './modules/shortcuts.js';
 import { openGallery, closeGallery } from './modules/gallery.js';
 import { refreshTasksView, openTasks, closeTasks } from './modules/tasks.js';