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/plugins/slideshow/slideshow.js

@@ -187,7 +187,7 @@ function renderImageSlide(slide) {
     const rects = slide.hotspots.map((h, i) => {
         const style = `left:${h.x}%;top:${h.y}%;width:${h.w}%;height:${h.h}%`;
         const label = resolveTargetLabel(h.target) || h.target || '';
-        return `<div class="slide-hotspot-live" data-hs="${i}" style="${style}" title="${escHtml(label)}"></div>`;
+        return `<div class="slide-hotspot-live" data-hs="${i}" style="${style}" data-tip="${escHtml(label)}"></div>`;
     }).join('');
     viewerSlide.innerHTML = `
         <div class="slide-image-wrap">