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/modules/notifications.js

@@ -73,7 +73,7 @@ export function render() {
             <span>${esc(i.label)}</span>
             ${i.dismissable !== false ? `<button class="upcoming-dismiss" data-dismiss="${i.id}"><i class="ph ph-x text-xs"></i></button>` : ''}
         </div>`).join('')}
-        <button id="dismiss-all" class="shrink-0 ml-auto text-t-dim hover:text-t-danger transition-colors" title="dismiss all"><i class="ph ph-x-circle text-sm"></i></button>
+        <button id="dismiss-all" class="shrink-0 ml-auto text-t-dim hover:text-t-danger transition-colors" data-tip="dismiss all"><i class="ph ph-x-circle text-sm"></i></button>
     </div>`;
 
     banner.querySelectorAll('[data-notif-id]').forEach(el => {