docs(ui): update help assets and regenerate help pdf

scripts/help-pdf.css

@@ -0,0 +1,96 @@
+/* Print stylesheet for docs/help.md → PDF (Chromium headless) */
+@page {
+  margin: 18mm;
+  size: A4;
+}
+html {
+  font-size: 11pt;
+  line-height: 1.4;
+}
+body {
+  font-family: "DejaVu Sans", "Liberation Sans", Helvetica, Arial, sans-serif;
+  color: #222;
+  max-width: 100%;
+}
+h1 {
+  font-size: 1.45rem;
+  border-bottom: 2px solid #333;
+  padding-bottom: 0.25em;
+  margin-top: 0;
+}
+h2 {
+  font-size: 1.15rem;
+  margin-top: 1.25em;
+  page-break-after: avoid;
+}
+h3 {
+  font-size: 1.05rem;
+  margin-top: 1em;
+  page-break-after: avoid;
+}
+code {
+  font-family: "DejaVu Sans Mono", "Liberation Mono", Consolas, monospace;
+  font-size: 0.92em;
+  background: #f3f3f3;
+  padding: 0.1em 0.35em;
+  border-radius: 3px;
+}
+pre {
+  font-family: "DejaVu Sans Mono", "Liberation Mono", Consolas, monospace;
+  font-size: 0.88em;
+  background: #f5f5f5;
+  border: 1px solid #ddd;
+  padding: 0.65em 0.85em;
+  overflow-x: auto;
+  page-break-inside: avoid;
+}
+pre code {
+  background: none;
+  padding: 0;
+}
+table {
+  border-collapse: collapse;
+  width: 100%;
+  margin: 0.75em 0;
+  font-size: 0.95em;
+  page-break-inside: avoid;
+}
+th, td {
+  border: 1px solid #bbb;
+  padding: 6px 8px;
+  text-align: left;
+  vertical-align: top;
+}
+th {
+  background: #eee;
+}
+a {
+  color: #1a5276;
+  text-decoration: none;
+}
+hr {
+  border: none;
+  border-top: 1px solid #ccc;
+  margin: 1.25em 0;
+}
+ul, ol {
+  padding-left: 1.35em;
+}
+li {
+  margin: 0.2em 0;
+}
+
+/* Images in docs/help.md */
+img {
+  max-width: 100%;
+  height: auto;
+  page-break-inside: avoid;
+  border: 1px solid #ccc;
+  border-radius: 4px;
+}
+p.help-figure-caption {
+  font-size: 0.9em;
+  color: #555;
+  margin: 0.35em 0 1em 0;
+  line-height: 1.35;
+}