feat: redesign help modal with accordion and clickable questions

- Replace flat list with <details>/<summary> accordion (5 categories)
- Questions are clickable: close modal → open chat → send question
- closeChatHelpAndAsk() helper bridges modal and chat panel
- Green accent on category icons and question hover
- Chevron arrows for expand/collapse state
- Dark theme support for all accordion elements
- Compact layout with no wasted space

static/css/04-interactive/_chat.css

@@ -298,6 +298,158 @@
     background: #1e8c4c;
 }
 
+/* ==========================================================================
+   Help Modal — Fullscreen Accordion
+   ========================================================================== */
+
+.chat-help-fullscreen .info-modal-content {
+    max-width: 560px;
+    max-height: 90vh;
+    overflow-y: auto;
+}
+
+.chat-help-intro {
+    font-size: 0.82rem;
+    color: var(--text-muted, #666666);
+    line-height: 1.5;
+    margin: 0 0 16px 0;
+    text-align: center;
+}
+
+.chat-help-accordion {
+    display: flex;
+    flex-direction: column;
+    gap: 6px;
+}
+
+.chat-help-group {
+    border: 1px solid var(--border-light, #e0e0e0);
+    border-radius: 6px;
+    overflow: hidden;
+}
+
+.chat-help-group summary {
+    display: flex;
+    align-items: center;
+    gap: 8px;
+    padding: 10px 14px;
+    font-family: 'Quicksand', sans-serif;
+    font-size: 0.85rem;
+    font-weight: 600;
+    color: var(--text-primary, #1a1a1a);
+    cursor: pointer;
+    background: var(--paper-secondary-bg, #f5f5f5);
+    list-style: none;
+    transition: background 0.2s;
+}
+
+.chat-help-group summary::-webkit-details-marker {
+    display: none;
+}
+
+.chat-help-group summary::after {
+    content: '';
+    margin-left: auto;
+    width: 6px;
+    height: 6px;
+    border-right: 2px solid var(--text-muted, #666);
+    border-bottom: 2px solid var(--text-muted, #666);
+    transform: rotate(-45deg);
+    transition: transform 0.2s;
+}
+
+.chat-help-group[open] summary::after {
+    transform: rotate(45deg);
+}
+
+.chat-help-group summary:hover {
+    background: var(--paper-bg, #ffffff);
+}
+
+.chat-help-group summary iconify-icon {
+    font-size: 1.1rem;
+    color: var(--accent-green, #27ae60);
+}
+
+.chat-help-questions {
+    display: flex;
+    flex-direction: column;
+    padding: 4px 8px 8px;
+    gap: 2px;
+}
+
+.chat-help-q {
+    display: block;
+    width: 100%;
+    text-align: left;
+    background: none;
+    border: none;
+    padding: 7px 12px;
+    font-size: 0.78rem;
+    font-family: 'Source Sans Pro', sans-serif;
+    color: var(--text-secondary, #333333);
+    cursor: pointer;
+    border-radius: 4px;
+    transition: all 0.15s;
+    line-height: 1.4;
+}
+
+.chat-help-q:hover {
+    background: var(--accent-green, #27ae60);
+    color: #fff;
+}
+
+.chat-help-footer {
+    display: flex;
+    align-items: center;
+    gap: 8px;
+    margin-top: 16px;
+    padding: 10px 12px;
+    background: var(--paper-secondary-bg, #f5f5f5);
+    border-radius: 6px;
+    font-size: 0.7rem;
+    color: var(--text-muted, #666666);
+    line-height: 1.4;
+}
+
+.chat-help-footer iconify-icon {
+    font-size: 1rem;
+    flex-shrink: 0;
+    color: var(--text-light, #999999);
+}
+
+/* Dark theme for help modal */
+.theme-clean .chat-help-group {
+    border-color: #333333;
+}
+
+.theme-clean .chat-help-group summary {
+    background: #2a2a2a;
+    color: #d0d0d0;
+}
+
+.theme-clean .chat-help-group summary:hover {
+    background: #333333;
+}
+
+.theme-clean .chat-help-q {
+    color: #999999;
+}
+
+.theme-clean .chat-help-q:hover {
+    background: #166b3a;
+    color: #fff;
+}
+
+.theme-clean .chat-help-footer {
+    background: #2a2a2a;
+    color: #777777;
+}
+
+.theme-clean .chat-help-intro {
+    color: #999999;
+}
+
 /* ==========================================================================
    Responsive
    ========================================================================== */