feat(ui): add tooltips to all pages — distillation, simulator, coach, deckgenerator

- Move .tip-icon tooltip CSS from training.css into global.css so all pages share it
- distillation.html: 8 param tooltips (Max Generations, Convergence Window, Supervised Epochs, Supervised LR, PPO Iterations, PPO Episodes/Iter, PPO LR, Min Win Rate Gate, Opponent, Playstyle) + ELO Ratings header
- simulator.html: tooltips on Opponent, Games, Record turn logs, API Endpoint, Model, Temp, Timeout
- coach.html: tooltips on Target Power Level, Meta Focus, Budget, Focus Areas, Find Similar Cards Results
- deckgenerator.html: tooltips on Target Bracket, Use my collection, Smart Substitution, AI Model

ui/global.css

@@ -864,3 +864,92 @@ body {
 .form-input:focus, .form-select:focus, .form-textarea:focus {
     box-shadow: 0 0 0 3px var(--accent-dim), inset 0 1px 3px rgba(0,0,0,0.1);
 }
+
+
+/* ══════════════════════════════════════════════════════════════
+   Tooltip System  (.tip-icon + data-tip)
+   Shared across all pages — do not duplicate in page-specific CSS
+   ══════════════════════════════════════════════════════════════ */
+
+.tip-icon {
+    display: inline-flex;
+    align-items: center;
+    justify-content: center;
+    width: 15px;
+    height: 15px;
+    border-radius: 50%;
+    background: var(--surface-3);
+    color: var(--text-secondary);
+    font-size: 10px;
+    font-weight: 700;
+    font-style: normal;
+    cursor: default;
+    position: relative;
+    vertical-align: middle;
+    margin-left: 4px;
+    flex-shrink: 0;
+    transition: background 0.15s, color 0.15s;
+    user-select: none;
+}
+
+.tip-icon:hover {
+    background: var(--accent-dim);
+    color: var(--accent);
+}
+
+.tip-icon::after {
+    content: attr(data-tip);
+    position: absolute;
+    bottom: calc(100% + 8px);
+    left: 50%;
+    transform: translateX(-50%);
+    background: var(--surface-0, #1a1a2e);
+    color: var(--text, #e0e0e0);
+    border: 1px solid var(--border, #333);
+    border-radius: var(--radius-md, 6px);
+    padding: 8px 12px;
+    font-size: 12px;
+    font-weight: 400;
+    line-height: 1.5;
+    white-space: normal;
+    width: 240px;
+    box-shadow: 0 4px 16px rgba(0, 0, 0, 0.4);
+    pointer-events: none;
+    opacity: 0;
+    transition: opacity 0.15s ease;
+    z-index: 1000;
+    text-align: left;
+    text-transform: none;
+    letter-spacing: 0;
+}
+
+.tip-icon::before {
+    content: '';
+    position: absolute;
+    bottom: calc(100% + 3px);
+    left: 50%;
+    transform: translateX(-50%);
+    border: 5px solid transparent;
+    border-top-color: var(--border, #333);
+    pointer-events: none;
+    opacity: 0;
+    transition: opacity 0.15s ease;
+    z-index: 1001;
+}
+
+.tip-icon:hover::after,
+.tip-icon:hover::before {
+    opacity: 1;
+}
+
+.tip-icon.tip-below::after {
+    bottom: auto;
+    top: calc(100% + 8px);
+}
+
+.tip-icon.tip-below::before {
+    bottom: auto;
+    top: calc(100% + 3px);
+    border-top-color: transparent;
+    border-bottom-color: var(--border, #333);
+}